Who are the 'tartan terrorists'?

Police said the instructions were 'cynically dangerous'

A man claiming to be a member of the Scottish National Liberation Army (SNLA) has said he sent two toxic packages to Downing Street and a Scottish MP. BBC News Online looks at the background to the organisation.

Dubbed 'tartan terrorists', the SNLA is one of a number of fringe organisations pursuing Scottish independence.

It was formed by a former soldier with the Argyll and Sutherland Highlanders called Adam Busby and engaged in low-level violence against English 'settlers' in the 1970s and early 1980s.

The SNLA has surfaced from time to time. It's obviously very tiny

Prof Paul Wilkinson
Terror expert

In 1983 there were 27 SNLA attacks, including letter-bombs to Margaret Thatcher and the Princess of Wales.

The letter to Mrs Thatcher was sent to a north London hotel where she was addressing 100 Conservative candidates.

Robert Key MP, the man who opened the package at the time, said: "The post came in and enclosed a package which just looked slightly odd and I recall making a small slit in the side of it and it was indeed a firebomb.

"If I had opened it wrongly, it would have been different, but it came from the SNLA and was later recognised to be the work of an anarchist, probably a loner, but it could have had serious effects."

Busby fled to Dublin after the 1983 letter-bombing campaign, where he reportedly tried to join forces with the IRA but the offer is said to have been refused.

Weapons 'stockpile'

In 1997, Busby was jailed in the Irish city for the campaign.

In recent years the group has made hoax bomb calls and death threats, some directed at the Royal Family.

The SNLA sent Prince William a fake anthrax bomb at St Andrews University last year.

The package was posted to the university's admissions office just weeks before the began his degree course.

The prince's university, St Andrews, was targeted by the SNLA

An attached note contained a code word and security forces were informed before the package was tested and declared to be harmless.

The SNLA was also investigated by the FBI after sending an identical package to a firm in Cape Cod which sold HP sauce to Britons living in the United States.

The group is now thought to be made up of a tiny number of militant extremists and individuals claiming to be members have been jailed for letter-bomb offences.

But experts doubt its claims to have a stockpile of weapons or a capability to kill any royals.

Following the latest events Professor Paul Wilkinson, an expert in international terrorism, said: "The SNLA has surfaced from time to time.

"It's obviously very tiny, in fact I understand the police are working on the theory it may have been just one individual behind this."