British interests abroad are more likely to bear the brunt of further attacks by al-Qaeda terrorists rather than the borough's synagogues or targets like Brent Cross shopping centre, according to a leading security think tank.

The last significant attack on a Jewish target in Barnet happened in 1994 when a car bomb exploded outside Balfour House at Tally Ho Corner, North Finchley.

The building was shared by a Jewish charity and an Israeli government department, but no lives were lost.

Two Palestinians — chemical engineer Samar Alami and electronics engineer Jawad Botmeh — were jailed for 20 years in 1996 for their part in this attack and another on the Israeli Embassy in London.

But former intelligence officer Ellie Goldsworthy, of the Royal United Services Institute, thinks north London is still not the most attractive target for groups like al-Qaeda. "Any attack in Britain would be likely to take place in London," she said. "But it is less likely that there will be an attack in the UK than on British interests outside the UK.

"Assets outside the UK are easier to get to. And by targeting populations such as the Turks, who have an ambivalent attitude to their government's relationship with the UK, they can achieve a double whammy effect.

"The US's line is that any country that harbours terrorists is a potential enemy of the US and can therefore be attacked. The terrorists are turning that on its head and saying that if you, like Turkey, work with the US or have British interests in your country then you are a legitimate target for attack."

In giving her view on why no al-Qaeda attack had taken place in Britain, she said: "Maybe they are planning something more ambitious. But it may also be that people aren't desperate to volunteer themselves as bombers."

The Community Security Trust (CSU), which organises security for Jewish sites, said it had stepped up security in the wake of recent bloodshed in Istanbul and added that police had increased their patrols around Jewish sites. Last month, two Iranian students were deported after the Sternberg Centre in East End Road, Finchley, was photographed in suspicious circumstances.

A Brent Cross spokesman said: "We have a permanent on-site police office and we take advice from the police on the level of risk on a daily basis."