If any evidence was needed of the London stock market's vulnerability when the FTSE 100 is above 6,600, then it was delivered yesterday.

A reasonably secure performance by all the FTSE indices during the morning, stimulated by Wednesday's good showing by Wall Street, was brought to a halt over lunchtime.

The FTSE 100, London's blue-chip benchmark, began to falter on news of a surprise rise in European interest rates. But another profits warning from Procter & Gamble, the US consumer goods group, tipped the index into negative territory for the rest of the afternoon, as the Dow Jones Industrial Average came under pressure. The Dow fell around 150 points during London hours.

And although the FTSE 250, SmallCap and Techmark 100 indices held on to some decent gains, dealers said there remained a worry that every time the 100 index pushed up towards 6,600, the institutions would rush in to book profits.

London was to a certain degree underpinned by the resilience of Wall Street's Nasdaq Composite index, which remained in positive territory while London was open.

The news that the European Central Bank had lifted euro zone interest rates by 50 basis points came as a considerable shock to global markets, which had expected a 25 basis points rise.

European stock markets lost their early gains and there was downside pressure on sterling.

There was a lot more nervousness surrounding the constituents of the Techmark 100 index, but it held up well to finish a net 20.46 firmer at 3,536.43.

Commenting on the London market, the UK strategy team at Deutsche Bank said: "In May, Deutsche analysts and the consensus produced more profit upgrades than downgrades. Unfortunately, the extent of upgrades and earnings growth still falls far short of what is being achieved in the US and Europe. With sentiment still negative and liquidity neutral at best it, is still not time to reduce the underweight rating in the UK."

It was another day of mixed performances from the leading UK stocks, with new and old economy stocks featuring in both the winners' and losers' league tables. Kingston Communications, Thus and Baltimore Technologies, all set to drop out of the FTSE 100 list from June 19th, featured in the winners, while the leading mortgage banks continued to suffer among the losers after the aggressive mortgage pricing initiatives undertaken by Standard Life and Nationwide, the mutuals.

Turnover in equities was a lowly 1.42 billion shares.