Campaigners object to HLS animal tests

But a defiant Mr Cass, nursing a three-inch head wound, said: "I am not going to give in to these intimidating tactics even if they do extend into this sort of violence."

Mr Cass said he noticed someone loitering about near his three-storey townhouse just before the attack and turned to see three people with baseball bats raised above their heads about to hit him.

A passer-by began chasing the people down the street after they assaulted Mr Cass, but he was sprayed with CS gas, said the managing director.

"I feel angry that there are people who pretend to be concerned about animals but then they go and attack someone in this sort of manner. It is totally hypocritical and cowardly," he said.

Heavily-built attackers

Mr Cass was taken to Hinchingbrooke Hospital in Huntingdon where he received stitches to his head wound and was treated for arm injuries.

An HLS spokesman said: "Security at Huntingdon remains as tight as it has always been and no doubt we will be giving staff further information on how to improve safety at home."

Natasha Taylor of protest group Stop Huntingdon Animal Cruelty (Shac) said: "We unreservedly condemn any act of violence be it against animals or humans."

But Mr Cass was highly sceptical of Shac's claims that the attack was not connected to its campaign.

"Obviously one can't say for certain but in my own mind there is no doubt that it was certainly perpetrated by supporters of that campaign," he said.

Police said two of the assailants were heavily built men - one wearing camouflage clothing, the other a baseball cap and a nylon padded jacket with a hood. The third is believed to be a woman.

Last month Huntingdon was saved from receivership over a £22.6m loan owed to Royal Bank of Scotland and two US banks, when it was backed by US investment firm Stephens Group.

But animal rights activists pledged to escalate protest actions against HLS, its customers and its financial backers.