The Royal Bank of Scotland is to pull the plug on a £20m overdraft with the controversial animal testing laboratory Huntingdon Life Sciences after bank staff were threatened by animal rights protesters. The Edinburgh-based bank's involvement with the laboratory is the result of its takeover of NatWest which had allowed the firm to borrow £22.5m to run its business. Industry sources confirmed last night the overdraft facility will not be renewed when the deal with RBS expires in August. The decision leaves the laboratory searching for new sources of crucial funding before the debt becomes repayable on August 31 and follows months of intimidation of the bank's staff by animals rights groups such as Stop Huntingdon Animals Cruelty. The overdraft facility was set up two years ago by NatWest around the time new management was installed at Huntingdon's laboratories after it was exposed for cruel treatment of puppies and told to clean up its act by the government.