The maps compare a former military airfield at Hollins Down in 1975 with the same site today.

Overall, the airfield has been transformed from a military installation into a centre for leisure, tourism and film-making, with much of its paved surface returned to nature. The perimeter road, the main gate, the woodland, the pond and the farmland in the south-east, however, are unchanged.

The most noticeable changes concern the runways. The shorter one, which ran from north-west to south-east, has been removed, and trees have been planted along most of its route. Only the eastern half of the main runway remains, now used by a gliding club, while the western half has become a wildflower meadow.

The buildings have also been given new purposes. The three hangars in the south have been converted into film studios, with a fourth, larger studio added beside them. The control tower now houses a café and visitor centre, and the barracks huts in the north-west have been demolished to make way for a hotel. In the south-east, the fuel depot has been replaced by a car park. Finally, a new access road has been built from the north.

Surveillance cameras have become a familiar feature of city life, and the latest systems can not only record what happens in a street but also recognise who is there. Although this technology undoubtedly helps to keep people safe, I believe that its disadvantages, above all for personal freedom, now outweigh its benefits.

The case for cameras is easy to understand. Recorded footage allows the police to establish what happened after an assault or a road accident, and it often provides more reliable evidence than the memory of a frightened witness. Visible cameras may also discourage minor offences such as vandalism on trains, and they help many people, especially those travelling alone at night, to feel more secure. Face-recognition systems promise to go further still, by locating a missing child or a wanted suspect in a crowd within minutes rather than days.

However, the ability to identify people automatically changes the nature of surveillance. A camera that merely records is checked only when something has gone wrong, whereas a system that recognises faces can build a continuous record of where every citizen goes, whom they meet and which meetings or protests they attend. Such information is extremely valuable to anyone who wishes to control a population, and powers introduced for one purpose are frequently extended to others. Even in democracies, people who know they are being watched may avoid activities that are lawful but unpopular, which quietly weakens public life. Large collections of facial images can also be stolen or misused.

On balance, therefore, I regard the spread of identifying cameras as more harmful than beneficial. Most of their genuine advantages could be kept if the law confined them to serious crimes under independent supervision, but without such limits, the price paid in privacy and liberty is too high.