Behind the surge were stories of a US takeover bid which at least enjoyed the distinction of being supported by American buying.
It was said Werthiem Schroder, the US investment house related to Schroders, the London securities group, was pursuing Micro shares.
This week Micro has surged 173p as the stories of US action gathered strength. The published turnover has not been extensive but for a heavyweight share there has been considerable activity.
A takeover bid for the software house would be a cause for jubilation for longstanding Micro shareholders. They have had an erratic ride since the shares arrived in the early 1980s. After a bright start the company ran into difficulties and it was not until 1989 that the shares really picked up steam. Four years ago they topped pounds 30 but as profits slumped fell away.
Last month the group, created by chairman Brian Reynolds, suffered the indignity of a pounds 6.5m loss but managed to assure the market that it was getting to grips with its problems.
The rest of the market had an uneasy session with New York's continuing weakness and the possibility of yet another Government by-election defeat having a deadening influence.
The FT-SE 100 index succumbed 23.2 points to 3,744.2 but the supporting FT-SE 250 index again succeeded in putting its more illustrious indicator to shame by scoring another record high, up 3.4 to 4,390.5.
British Petroleum, with the crude price even stronger, remained in demand, hitting 591.5p with a 5.5p gain.
British Steel, however, fell 3p to 190.5p with SGB Warburg downgrading and sending out a sell signal. RTZ, on firmer metal prices and positive comments from Lehman Brothers, improved 15p to 973p.
Amstrad, the electric group, had a difficult session, losing 6p to 172p but Sage, the computer group, made further headway, up 4p to 418p.
Manchester Utd scored a 22p gain to a 346p peak as Merrill Lynch made positive noises and Cliveden, the upmarket hotel group, made a solid debut, closing at 86p from a 73p placing.
The arrival of Texas Homecare man John Coleman as chief executive of the struggling House of Fraser stores chain was greeted with 14p slide to 175p on the theory the hoped for take over bid would, at least, be delayed.
WH Smith climbed a further 8p to 484p on disposal hopes and attempts to put forward Sears as a takeover candidate soon petered out, leaving the shares 1.5p down at 98p.
Matthew Clark, the drinks group which has emerged as the UK's second largest cider maker, edged forward 6.5p to 744.5p as Credit Lyonnais Laing said it was a "superior cash generator". Profits for the year ending this month are likely to be pounds 25.5m with pounds 82.9m seen for 1988.
Building and related shares continued to draw strength from the mortgage war and waters were buoyed by the government sales. Paper and packaging was ruffled by the cautious comments from Jefferson Smurfit. Rentokil's higher offer for BET clipped its shares 13p to 350p; BET was a shade firmer at 208.25p
Mentmore Abbey returned at 8p against the 6.5p valuation for the pen group's pounds 24.5m takeover of Abbey, a storage group. Corporate Services held at 141p; its cash call to help the pounds 47.8m takeover of the Blue Arrow recruitment chain received a 91 per cent take up.
B Elliott, once a leading machine tool group, now a niche engineer, put on 5p to 83p as NatWest Securities said it was about to rejoin the mainstream engineering sector and said buy.
Zotefoams, the chemical group hit by destocking, held at 268p; ABN Amro Hoare Govett forecast a modest profit advance to pounds 7.5m this year with pounds 9.6m next.
MultiMedia shaded 1p to 84p. Meglomedia, the media group headed by Maurice Saatchi, has taken a 10 per cent stake. The shares come from Monaco-based 1960's whiz kid David Rowland whose Inoco property group retains 15.66 per cent. Mr Rowland has accepted Meglomedia shares in exchange and has a 6.41 per cent interest.
Aegis, the media buyer, rose 3.25p to 53.5p on bid talks and Sentry Farming continued to enjoy its results, up 33p to 251p.