A benefactor about whom little is known other than his name has left almost £4 million to help children with special needs in Wiltshire.

William Couch arranged for the money to be placed in a trust after his death. Now around £100,000 a year will be spent on educational projects.

Mr Couch who was known as 'Doc' left the money to Wiltshire County Council on condition that details about his identity and address were kept secret.

Much of his £3.8 million estate results from a single share holding in the pharmaceutical giant Glaxo Wellcome. That alone has been valued at £2.7 million. There are 64 other holdings.

It is understood that Mr Couch registered a trust fund with the council some years ago by paying an administration fee of £100.

The full scale of the endowment only become known recently when his widow died and the estate was settled.

Now county council officers who are charged with administering the trust are in discussions with solicitors and the Charity Commission. They are also speaking to their colleagues at Swindon Borough Council about how the money will be distributed.

County treasurer David Chalker told the county council's investment sub-committee that he has appointed Schroder Personal Investment Management to take over the investment.

He said: "It is disposing of these investments, with the aim of reinvesting the proceeds in a more balanced portfolio."

He said the bequest came out of the blue. It was specifically to provide educational help for Wiltshire children with special needs.

Councillors are being asked to set up a special management committee to act as trustees of the trust.