BLUE-CHIP shares notched up gains for the fourth straight session yesterday but mid-caps stole the show at the London stock market, soaring on the back of a weaker pound in dull, pre-holiday trading. Financial markets will closed in London and New York on Monday.

The FTSE-100 benchmark index bounced up and down for much of the day before closing near the session's best levels - 20 points, or 0.3%, better at 5955.6. Decliners were in a three-to-two majority.

Share price movements were exaggerated by thin volumes. Total market turnover was relatively subdued at 830 million shares with 60% targeted outside the top 100 shares.

The City was not surprised by the upward revision of the gross domestic product figure for the first three months of the year.

Second-liners were the big story of the day with the FTSE-250 mid-cap index ending 43.3 points firmer at 5897.8.

Gilts finished stronger after a late spurt before the holiday weekend. June futures settled 0.16 higher at 108.54.

Across the Channel, German shares roared ahead to close at a fresh record amid speculation about mergers in the banking sector and talk of a bid from the Axel Springer Verlag publishing empire for the UK's Mirror Group Newspapers. In London share dealing, Mirror Group shares jumped by 6.5p to 218p.

Among other big Footsie 100 risers was Railtrack, up 23.5p to 1230p, as City sentiment about the future for the privatised rail industry continued to improve.

Scottish-based transport group Stagecoach was 72.5p higher at 1368p, Go Ahead was up 21p to 722.5p, and National Express was also 20.5p up to 1107p. However, not all transport stocks were pulling ahead.

British Airways launched Go, its new no-frills airline, but BA shares fell after investors learned that American competition authorities want to place new restrictions on its planned alliance with

American Airlines.

BA's shares fell 1.5p to 647.5p as a result, although airport operator BAA rose 23.5p to 678p as investors factored in likely increases in traffic through its airports as the budget flight market expands.

Struggling cider maker Merrydown jumped 3.5p to 50p after it unveiled a package of changes aimed at restoring its fortunes. Rival Bulmer was unchanged at 356.5p.

Computacenter, which floated on Thursday, saw shares slip back 25p to 741p, still well ahead of its 670p float price.

Elsewhere in the information technology sector, Misys - now a member of the FTSE-100 - was down 37.5p to 3381.25p, Sage Group rose 15p to 1518p, and Eidos surged 22.5p to 1242.5p.

Biocompatibles rose 6p to 147.5p after it announced a #29m share placing and open offer to fund the commercialisation of its medical technology.

More Group, which now looks set to fall into the hands of American company Clear after a rival bid from France's Decaux was referred to the MMC yesterday, slipped 7.5p to 1122.5p.