Luton County Court is to be the scene for an appeal which, if successful, could spawn a major new class action in respect of alleged medical negligence over the prescription of human insulin for diabetics.

The pending hearing is a unique case brought by litigant-in-person, Derek Beatty, 46, who was diagnosed a diabetic when he was 28 years old. Beatty claims that a change in his prescription 12 years ago from animal insulin to human insulin resulted in, inter alia, a complete personality change.

Now he is suing doctors who he claims wrongly prescribed the change in insulin in the first place and then failed to diagnose that the symptoms he began suffering from were side-effects of the new drug.

Beatty, a healthcare consultant, says that if his claim succeeds it will be worth over £250,000. This takes into account the pain and suffering he claims he has been unnecessarily put through as a result of the side-effects of the drugs, the break-up of his marriage, the loss of his children as an ancillary to the breakdown of his marriage and £50,000-worth of legal costs which were run up in divorce proceedings.

He says the "side-effects" he suffered included a personality change, aggressive behaviour, acute perspiration, muscular cramp, skin disorders, tendonitis and depression. He has since been put back on animal insulin and says the symptoms have disappeared.

His claim was dismissed when it came up in St Albans County Court, on the basis he had insufficient medical evidence to back up the allegations he was making. Now though he is appealing to Luton County Court against that ruling. He says that if he fails there he is prepared to take the matter on to the Court of Appeal and the House of Lords.

Beatty says his claim is the tip of an iceberg. He claims that as many as 70 deaths of diabetes sufferers in this country could be attributed to a change in the type of insulin, and believes there are well over 900 people who could be waiting in the wings to launch action similar to his if he wins.

He says that though in the past claims over insulin have been made against the pharmaceutical industry rather than individual doctors, he believes it is the doctors who should be the target.