Scott Wilson, a senior UK Home Office official and national co-ordinator of the Protect and Prepare counter- terrorism programmes,told the Security and Counter Terror Expo here that these suspects pose a "high risk" to Britain.
I cannot answer where it is going to go. It [the terrorism threat] is going to be with us for a long, long time," he said this week.
According to The Times, he indicated that a fifth of the 350 so-called returning terror suspects were "high threat" extremists and are suspected of plotting or wanting to carry out attacks in Britain.
More than 800 British extremists are believed to have joined ISIS in Iraq and Syria.
Meanwhile, an analysis by 'The Daily Telegraph' found that one in three terrorists convicted of plotting attacks on British soil were able to enter the UK after training abroad.
Preliminary research by the Henry Jackson Society think-tank and the newspaper found that of the 77 Britons convicted of major terror plots or attacks which posed an imminent threat to life since 1999, 27 had become trained or fought overseas in war-torn countries.
An examination of the major attacks and plots in the UK over the 15 year period found that 10 of the 13 ringleaders had travelled abroad for training or combat experience and returned to the UK.
Indian-origin MP Keith Vaz, the House of Commons' Home Affairs SelectCommittee chairman, said: "These figures are extremely concerning andwhat they show is that people are leaving our country without theauthorities knowing that they are going.
