Not many of us like the thought of being watched all the time, but those who live in cities face that prospect. CCTV cameras have been with us for two decades or more, but their numbers have greatly increased. Since the London bombings new ones have been sprouting up, so that a stroll around the block in central London can put you on 37 separate TVs.

Now the BBC reports on the development of eternal planes, lightweight and solar powered, which stay aloft permanently beaming down their pictures of what is going on below.

Unmanned surveillance vehicles are increasingly evident in a world that relies on knowing what people and places are doing. Unmanned Aerial Vehicles (UAVs) patrol innocuous-looking skies and silently report back streams of strategically important data, video, and images from locations around the world.

We are used to satellite surveillance, and this is only an extension which gives lower cost and higher definition coverage, with the potential to cover greater areas. It makes for a very different world from that in which people could go about their business without too much snooping from the authorities. People in Britain have largely accepted the changes, insofar as they are aware of them, as the price of their protection from criminals. It is debatable whether CCTV cameras cut street crime or move it elsewhere, but their role in solving crime has been evident, featuring many high profile cases. This included the Harrod's IRA bombers, the James Bulger child murder case, the Charing Cross gay murders, and the white racist hate bomber. Many less publicized crimes can be added.

In the recent London bombings the surveillance cameras enabled the bombers and attempted bombers to be identified, and the failed ones arrested before they could try again. This will probably lead to the bomb-makers and controllers being detained, preventing further terror strikes. Most people seem ready to credit the authorities for their swift detection work.

There has long been a tradition that those in authority should not know any more about our activities than is strictly necessary, and we have valued the right to keep them out of our lives. We have regarded the claim that "only the guilty have anything to fear" as the excuse of tyrants everywhere. It looks increasingly, though, that a combination of terrorism and new technology is changing that equation. People in Britain, at least, seem prepared to accept more intrusion as the price of their protection.