The four-day rally in London's benchmark index, the FTSE 100, ground to a halt yesterday. And just as the rally had mostly been triggered by a return of confidence in many of the TMTs (telecoms, media, technology), it was that area that was behind yesterday's sharp fall.

The catalyst for the latest bout of weakness in TMTs was a profit-warning from Dimension Data, the South Africa-based information technology group. The impact of the DiData news ran right through the stock market, but the heaviest punishment was in the FTSE 100 which gave up all and more of Monday's rise, eventually finishing a net 76.8 lower at 5,639.9. It was the same story in the mid and SmallCap indices, which were also hit hard by the fear of more profit warnings and bearish news from the TMT areas.

At the close, the FTSE 250 was down 3.3 at 6,285.8, having been down 13.5 earlier. The SmallCap index was always under pressure and finished the day 6.6 off at 2,922.7.

But the worst individual performance of the main indices came from the Techmark 100 index which fell 3.7 per cent as investors registered renewed alarm over the potential for more scares from the high tech areas.

Dealers said it was mostly the DiData story which had punctured the market's new-found third-quarter confidence, although the latest flurry of profit warnings from the US did nothing to bolster sentiment.

Wall Street played only a minor role in London's worryingly weak performance, although there were more US profit warnings preying on the minds of UK investors.

While the TMTs were on the back foot, it was mostly old-economy stocks in the winners lists. Kingfisher held up well as the group announced the sale of Superdrug and the demerger of the Woolworths business. Somerfield, the food retailer, topped the 250 winners' list after a positive trading update. Turnover in equities was 1.93 billion shares.