The London business, which specialises in power cables and other electrical components, said a "general softening of demand" for its products would hit sales and profits. The shares fell 51¼ - or 37pc - to 89p, wiping £20m off the company's value and £5m from Mr Rothschild's fortune. In its latest profit warning, Volex said the recent dip in demand had not affected its largest customer, but that sales were now likely to between $470m and $485m, compared to earlier analyst forecasts of $529m. Operating profits are now on track for between $11m and $14m. Mr Rothschild declined to comment.