IELTS Academic Reading Practice Test 261

In the summer of 1939, a small group of academics, chess players and linguists began arriving at a Victorian country house in Buckinghamshire. Bletchley Park had been bought the previous year for the Secret Intelligence Service by its chief, Admiral Sir Hugh Sinclair. It was chosen partly because it stood at a railway junction with lines to both Cambridge and Oxford, from which mathematicians could be recruited. The Government Code and Cypher School moved there in August, shortly before Britain declared war, and the site soon became known as Station X.

The main target was Enigma, a German machine that looked like an oversized typewriter. Each time an operator pressed a letter, an electric current passed through rotating wheels, a reflector and a plugboard, and a different letter lit up. The settings changed every day, so the same message enciphered twice produced entirely different text. Enigma had, however, been broken before the war: Polish mathematicians had reconstructed the machine and had been reading German traffic since the early 1930s. In July 1939 they passed everything they knew to British and French intelligence at a meeting near Warsaw.

The central tool was the bombe, an electromechanical machine designed by Alan Turing and improved by Gordon Welchman, whose diagonal board greatly reduced the number of false results. Each bombe contained banks of drums that imitated the wheels of an Enigma machine and whirred through possible settings. When a combination produced a plausible piece of German, it was printed out and checked by hand. The first bombe reached Bletchley in March 1940. By the end of the war more than two hundred were in use, most of them at outstations staffed largely by women of the Women's Royal Naval Service.

Work was divided between wooden huts built in the grounds. Hut 6 dealt with the messages of the German army and air force, while Hut 8, where Turing worked for much of the war, attacked the naval cipher. Decrypted texts passed to Hut 3 and Hut 4, where translators and analysts decided what mattered, and their reports went to London under the cover name Ultra. Secrecy was obsessive: staff were told nothing beyond their own task, and a typist might handle German text for years without learning where it came from.

Naval Enigma was the hardest problem, because the German navy used extra procedures and kept its code books aboard ship. Progress came from captures. On several occasions boarding parties took key lists and settings from damaged U-boats, sometimes at the cost of sailors' lives. These seizures allowed Hut 8 to read convoy traffic for weeks or months at a time. During 1941 and 1942 the resulting intelligence helped the Admiralty to route merchant ships around the patrol lines of the submarines, and it contributed to the hunt for the Bismarck in May 1941.

Enigma was not the only German cipher. The high command used a far more complex machine, later called Lorenz, which printed its output as a stream of letters. It was broken without anyone ever seeing it: a young mathematician, Bill Tutte, deduced its internal structure from patterns in intercepted traffic. Reading Lorenz messages required enormous computation, and the answer was Colossus, an electronic machine built by the Post Office engineer Tommy Flowers at Dollis Hill and installed at Bletchley early in 1944. Colossus is widely regarded as the first programmable electronic digital computer.

By 1945 around ten thousand people were working for the codebreaking organisation, three-quarters of them women. Some were mathematicians and linguists; far more were clerks, radio operators, engineers and mechanics. Recruitment was done quietly through universities, schools and personal contacts, and few of those approached were told what the work would be. The mixture of disciplines was one of the organisation's strengths: classicists worked beside statisticians, and chess players proved unusually good at spotting patterns.

The contribution to the war is difficult to measure, partly because few records survive and partly because intelligence works only if someone acts on it. Its clearest effects were at sea, where convoys could be diverted from known patrol lines, and in the Mediterranean, where knowledge of German supply shipments helped the Royal Navy to intercept them. Before the Normandy landings in June 1944, Ultra gave the Allies a detailed picture of German dispositions and of the enemy's belief that the attack would come elsewhere.

Then, almost overnight, it stopped. The people who had worked at Bletchley went home and said nothing. Some continued in intelligence, but most described their war years vaguely, if at all, and the machines were dismantled and the papers destroyed. The silence held for nearly thirty years. It was broken in 1974 by a former officer, Frederick Winterbotham, whose book The Ultra Secret announced the story to a startled public. From 1979 the official history of British wartime intelligence began to appear.

Bletchley Park is now a museum. The huts, many of which had been allowed to decay, have been restored, and the site receives visitors in large numbers throughout the year. Turing, who died in 1954, received an official pardon in 2013. The long reserve of secrecy that surrounded the codebreakers has become one of the things that makes their story so attractive.

For more than two thousand years the walls of a city were the strongest argument in warfare, and the machines built to break them were the heavy artillery of the ancient and medieval world. The trebuchet was the most sophisticated of them. Where a catapult stores energy in twisted rope or a bent bow, a trebuchet uses gravity: a great weight falls, and its energy passes through a pivoting beam to a stone or a container of burning material. Two forms existed. The older one, driven by a team of people hauling on ropes, was known in Europe as a mangonel, a word borrowed from the Arabic manjaniq. The later form, in which the hauling is done by a suspended counterweight, appears in Mediterranean sources in the twelfth century, and armies arriving from western Europe during the Crusades soon met it in the eastern Mediterranean.

The man-powered machine seems to have originated in China, where it was used both on the battlefield and at sieges, and it travelled westwards with Islamic armies before reaching Europe. Its advantage was speed. A trained crew could load and release every few seconds, and because the whole machine was light enough to be carried on a cart, it could accompany an army on campaign. Its weakness was that the weight of the projectile was limited by the number of people who could pull at once; a large engine might need dozens of ropes and a correspondingly large team, and the pullers had to be drilled to act together. Stone-throwing of this kind was therefore most effective against wooden defences, rooftops and the people inside a town rather than against thick masonry. Its beam was usually a single trunk, chosen for flexibility as much as for strength, and much of the machine could be assembled by local carpenters from timber cut nearby.

The counterweight machine was a different order of engineering, and surviving accounts suggest that no two were quite alike. Its beam, a massive baulk of timber perhaps ten metres long, rested on an axle supported by a heavy frame of uprights and braces. The short end carried the counterweight, a box or a hinged bin packed with stones, lead or earth, sometimes weighing several tonnes. From the long end hung the sling, two ropes joined to a leather pouch that held the projectile. A hook on the beam's tip released one of the ropes, letting the pouch open at the right moment. To prepare a shot, a winch wound the long arm down to the ground; the crew loaded the pouch, and the release of the winch allowed the counterweight to fall and the arm to sweep upwards.

What made the machine effective was the relationship between the two arms. The counterweight falls only a short distance while the tip of the long arm travels through a wide arc, so a modest movement of a heavy mass is converted into a rapid one of a comparatively light one. The sling adds a second multiplication. Whipping over the top, it increases the speed of the stone still further before letting go, and the angle at which the stone leaves can be adjusted by shortening the sling, moving the axle or altering the length of the hook. A well-built machine, experiments suggest, could throw a stone of a hundred kilograms or more a distance of two hundred metres, while a lighter projectile travelled considerably further. The stone itself was usually a dressed ball of limestone or sandstone, since a ragged lump would tumble in the air and lose both range and accuracy.

Almost everything known about these machines comes from three kinds of evidence, none of them straightforward. Chronicles describe sieges and sometimes name the engines, but their authors were rarely engineers, and the distances they report are frequently implausible. The most quoted anecdote concerns the siege of Stirling Castle in 1304, when Edward I of England is said to have refused a surrender until his new machine, the Warwolf, had been tried. Financial records are more sober: they list payments for timber, rope, carts and the wages of the men who built and worked the engines. Physical traces are the scarcest. The machines were made of wood and rope and have long since rotted, though numbers of rounded stone balls, dressed to fit a pouch, have been found at castle sites, and a few waterlogged timbers have survived in ditches.

Modern understanding owes much to people who have built the machines again. Engineers and enthusiasts have constructed full-size trebuchets at castles in Britain, France and Denmark, and their experiments have settled several arguments. They have shown, for instance, that a sling is not a refinement but a necessity: without it, the range falls sharply. They have also demonstrated how sensitive the machine is to small adjustments, so that a crew would have had to sight a shot by trial rather than by calculation. What the replicas cannot settle is the accuracy of medieval reports of enormous ranges, since a modern machine built with steel fittings and a carefully measured counterweight is not quite the improvised, frequently repaired object that stood outside a besieged town.

Few arguments in the heritage world are as bitter as the one that breaks out whenever a famous place is fenced off or closed. The painted cave at Lascaux in south-western France was closed to the public in 1963, when algae began to spread across its walls. Altamira, in Spain, has been opened and closed several times since.

Each decision provoked anger, and each was justified by the same claim: that the site was being loved to death, and that the only way to save it was to keep people out. Meanwhile the number of people visiting museums, monuments and archaeological sites around the world has risen year after year for half a century.

The case for closure rests on a simple asymmetry. A wall can be rebuilt and a garden replanted, but the surface of a prehistoric painting or the carving on a stone cross cannot be restored once it has been worn away or coated in mould. Visitors change the air inside a cave simply by breathing, raising the temperature and the humidity and feeding the micro-organisms that attack the pigment. Even the oils from a hand can leave a mark that will not fade. Where the fabric of a site is unique and the science that might explain it is still developing, there is a respectable argument for keeping people away until better methods exist.

Yet the argument is rarely as one-sided as it appears. Heritage is expensive, and much of the money that pays for the upkeep of historic buildings, the excavation of buried remains and the training of conservators comes from the people who visit them. Guardianship is not free, and a closed gate does not remove the cost of a roof, a warden or a drainage system. A site that is closed may be protected, but it must then be paid for by somebody else. In countries where public budgets for culture are shrinking, the choice is often between visitors and neglect.

There is also a question of justice. Great monuments belong to everyone, not only to those who can afford to travel, and a policy of closure converts a public inheritance into a private one, available to the specialist and the wealthy. That said, the distribution of visitors is itself unequal: a handful of famous destinations absorb the crowds while hundreds of equally interesting places nearby are ignored. Closing a celebrated site may simply push the pressure elsewhere, which protects nothing and damages more. Hotels, guides and drivers in the towns around a famous monument depend on the visitors it draws, and their livelihoods are rarely considered when a closure is announced.

One reason the debate is so heated is that the blame is misplaced. Studies of historic buildings, coastlines and buried archaeology consistently show that the most serious threats come not from tourists but from neglect, changes in land use, drainage, road building and, increasingly, extreme weather. A single winter of heavy rain may do more to a Roman mosaic than decades of guided tours. Visitors are visible and easily counted; a leaking gutter or a plough that cuts through a buried settlement is not, and attention follows what can be photographed. It is easier to blame a coach party than to argue with a highway authority.

The response of many site managers has therefore been to control numbers rather than to eliminate them. Timed tickets, guided groups, raised walkways, glass screens and the careful routing of people through a building can reduce wear dramatically while allowing the public in. Where a particular room or chamber is exceptionally fragile, it can be closed while the rest of the site stays open. Carrying capacity, the maximum number of people a place can absorb without harm, is difficult to establish but can be estimated, and it gives managers something to work with. Monitoring, rather than assumption, tells them which of these measures is actually needed.

Replicas have their place in this. The copy of Lascaux that opened nearby in 1983 allows visitors to see the paintings in conditions the original could never tolerate, and casts and digital reconstructions have made inaccessible objects available to millions. But a replica is an interpretation, not a substitute, and I am uneasy when a convincing copy is used to justify closing an original for good. What such a copy conveys is the skill of the people who made the paintings, not the presence of the place itself.

That is why I would make closure the last resort rather than the first response. It should be time-limited wherever possible, reviewed at fixed intervals, and justified by published evidence rather than by the instinct that visitors are always a danger. Where a site must be shut permanently, the decision should be taken openly, with the reasons explained and the loss acknowledged. Above all, those who manage these places should be honest about what is being traded against what.

None of this is an argument for allowing crowds to do as they please. Some places are so fragile, and so poorly understood, that any access is too much. But such places are fewer than the headlines suggest, and the temptation to win an argument by closing a gate is one that heritage bodies should resist. The question is not whether we should protect these places, but how many people we are prepared to let see what we are protecting.