Terrorism plots in Britain are becoming less complex, involving fewer participants, an official watchdog has said.
The independent reviewer of terrorism legislation, David Anderson QC, said the security services were no longer seeing ambitious plots to inflict mass casualties, like the 7/7 attacks on the London Underground.
However he cautioned that the emergence of "lone actors" and self-organised plots against relatively limited targets could be more difficult to detect and stop.
"We are certainly not seeing now what we saw in the years around 2005, 2006, which are the large, ambitious, 9/11-style plots perhaps to bring down simultaneously several airliners," he told the BBC Radio 4 Today programme.
"What we are seeing is a trend towards lone actors and we are also seeing self-organised plots.
"It may be that what we are seeing is something getting a little closer to the position that still applies unfortunately to some extent in Northern Ireland which is smaller scale, lower tech attacks on national security targets more than the general public. As Northern Ireland shows, they can be very difficult to anticipate and to stop."
He stressed however that the emerging trend did not mean that the threat from al Qaida was over.
"Al Qaida has been diversifying or fragmenting - particularly in the Yemen. Al Qaida in the Arabian Peninsula do still have good technicians and they have people who can make bombs. So we are not out of the woods," he said.
Mr Anderson, who publishes his annual report on Wednesday, also defended the controversial European Court of Human Rights, insisting its ruling had not jeopardised security in the UK.
"If you look at what the European Court actually says in terrorism it is good news because it has modified the more rigorous and objectionable aspects of our laws without, I think, decreasing our safety in any way," he said.