Internet network company Bookham Technology may be relegated from the FTSE 100, the London share index, after its shares tumbled amid concerns about its third-quarter results.

Bookham, based at Milton Park, near Abingdon, said it could see no reason for the fall in its share price, which knocked the value of chief executive Andrew Rickman's family holding to less than £500m, against a high in July of above £1.5bn.

Investors who bought shares in a new issue in September at £33.50 saw the shares halve.

Mr Rickman said he was "bemused" by the market reaction to the third-quarter figures.

"The results were very positive and ahead of expectations," he said, pointing to 83 per cent growth in quarter-on-quarter revenue.

By yesterday, the shares had recovered to just above 16.