A SWINDON animal rights activist's name was written on one of the letter bombs posted in the last few weeks.

Barry Horne, who used to live in Goddard Park, Old Town, died in 2001 after going on a hunger strike while serving an 18-year sentence for a fire bombing campaign.

Police have revealed his name was in one of the letter bombs posted out a fortnight ago.

The name of a second campaigner, who is still alive, was scrawled on the back of one of the Jiffy bag-style envelopes sent to forensic science laboratories last month.

They were all posted on January 18 to forensic laboratories in the Oxfordshire and West Midlands area. One was involved in paternity testing, another was the Government-owned Forensic Science Service headquarters in Birmingham.

The name of the second activist is not being released by police.

It appears to strengthen the theory that animal rights activists are behind the campaign.

Police are examining this as a "priority line of inquiry" along with the idea that a disgruntled motorist could be responsible.

Six of the seven companies who have been targeted in the last three weeks are involved in providing services or technology to law enforcement agencies.

The other main theory is that someone enraged by Britain's growing surveillance society could be behind the attacks.

The police's National Co-ordinator for Domestic Extremism, Assistant Chief Constable Anton Setchell, is leading the inquiry.

A spokesman for him refused to comment today on a report that the current campaign has similarities to a previous campaign last summer, during which a home-made device was sent to the office of the Labour Party in Cambridge.

Detectives on the current inquiry are said to be liaising with Cambridgeshire's police force as they examine other past letter bomb attacks.

No-one has been arrested so far in connection with the investigation, which escalated in seriousness earlier this week when three letter bombs exploded in consecutive days.

In each case, the bombs have been homemade pyrotechnic-style devices contained in A5 jiffy bags. At least two contained glass.

In addition to the three sent to forensic laboratories last month, another three were posted to traffic enforcement companies in London, Berkshire and south Wales this week.

They included the Driver and Vehicle Licensing Agency in Swansea and the offices of Capita, which runs London's congestion charging system.

The other was sent to a house used as a business address in Folkestone, Kent, on Saturday. At least nine people have been injured in the blasts.