Paul Wilkinson: This doesn't mean they have given up on bombing

Although jihadi extremist groups have kidnapped British Muslims in Iraq, we have no experience of them kidnapping any member of the armed forces on United Kingdom territory.

This doesn't mean they've given up the idea of bombs or suicide attacks on transport systems. If proven, this plot would mean a new element in the repertoire of terrorism. This would not mean they have given up on mass killing, but I think it's clear from the experience in Iraq that they managed to extract enormous publicity from this type of event. They used the internet to send images of the kidnap victims under great pressure, possibly pleading for their lives, and being threatened with execution.

In Iraq, the terrorists assumed that would put enormous pressure on the families, of course, but also the wider communities and on the authorities because of the demands there would be for some concessions for the terrorists in order to get the victim released.

If a Muslim serviceman was targeted, as alleged, this would have added significantly to the symbolic value - the person concerned joined the British armed forces and thereby "betrayed" their membership of the Muslim religion. So the message would have been, if you co-operate with British armed forces you are putting yourself in a position where you may well be punished. That's a type of terror tradition to intimidate not just the individual victim and their family, but to send a wider message of terror to the general community.

If reports of the alleged plot are correct, it is important to think about the measures that should be taken to enhance the protection of our service personnel.

Professor Paul Wilkinson is chair of the advisory board of the Centre for the Study of Terrorism and Political Violence at St Andrews University