Oil producer BP kept the London market in the red yesterday after investors lost the right to the most recent dividend payout.

Shares in the UK's largest company fell two per cent on a day when stocks going ex-dividend filled the top five places on the fallers board of the FTSE 100 Index.

With heavyweights such as Centrica and Tesco among the five, it was no surprise that the Footsie ended the session down 21.1 at 5439.8.

Centrica weakened 5p to 242p, BP dropped 13p to 627p and Tesco fell 6p as investors moved out of the stocks.

The loss of recent dividend payments also explained why insurer Royal and Sun Alliance faded two per cent, or 1p, to 104p.

BAA was also on the slide after revealing that the passenger load on planes using its airports had fallen since the July 7 London bomb attacks.

Its shares weakened 9p to 629p, although there was some buying of the stock during the afternoon as investors felt the initial reaction to the news was overdone. The airports operator was joined in the red by mobile phone company Vodafone as investors took the opportunity to bank profits after its shares hit their highest level in a month on Tuesday.

Shares in Vodafone drifted 1p to 150p.

AstraZeneca weakened 26p to 2569p after broker Credit Suisse First Boston downgraded it to "underperform" from "neutral", while analysts also noted the drugs company was ready for a legal showdown with an Israeli competitor seeking to make copies of its best-selling schizophrenia treatment.

But there were gains for companies due to update the market on trading today.

Brewer SABMiller lifted 8p to 1081p and telecoms operator BT advanced 2p to 214p.

Recovering retailer Marks and Spencer was also in buoyant mood following good results on Tuesday and the news that design guru George Davies would stay with the company.

Shares were up 8p at 443p - well ahead of the 400p that Philip Green was willing to pay for the company. JP Morgan raised its target price for the stock to 470p from 450p.

Argos owner Gus was strong in the retail sector - 8p ahead at 870p - but fellow retailer Next was stuck at its opening mark of 1350p and Kingfisher slipped 2p to 219p.

Outside the top flight, transport operator FirstGroup rose 4p to 339p after reporting a strong showing by its rail operation, despite the London terror attacks having a significant impact on business.

Logistics group Wincanton was also upbeat after announcing that profits had nearly doubled in its first half after it won contracts with blue-chip companies.

Shares advanced 13p to close at 330p.

Among the day's best performers were Tate and Lyle, up 11p at 496p, PartyGaming, up 2p at 90p, Antofagasta, ahead 31p at 1511p, and Kelda, which had climbed 13p to 710p by the close of business.