The index surged 140.5 points to 5,599 with Glaxo Wellcome and SmithKline Beecham providing a massive injection. Glaxo rose an incredible 20.7 per cent with a 340p gain to 1,983p (after 2,100p), and SB put on 65p to 845p (950p).
Ten minutes after the market opened Footsie was riding above 5,600, up 157, largely on the delirium evident in the shares of the new drug alliance.
As Glaxo and SB lost a little of their euphoria the market's hunt for other mega-merger candidates lifted Footsie constituents.
Not surprisingly Zeneca emerged as the favourite bid target. The drugs group, often linked with Swiss giant Roche as well as Glaxo in recent years, jumped 235p to 2,685p. At one time it was 355p higher. Nycomed, the result of last year's merger between Amersham International and Norwegian group Nycomed, rose 100p to 2,500p.
Footsie's gain was the best since September last year when the story appeared that the Government was becoming more favourably disposed towards Britain's EMU involvement.
Trading in Glaxo and SB, which together will enjoy the market's largest capitalisation, and the perceived bid candidates was heavy.
But the drug-induced euphoria failed to spread through the rest of the market where volume was often modest. The Midcap index, representing the 250 shares immediately outside Footsie, managed a 16.9 gain to 4,878.4; it is 65 points below its peak, hit in October. The Smallcap did manage a new high, gaining 12 to 2,384.7.
The latest Footsie burst only tended to reinforce the yawning gap which has developed between blue chips and the rest of the market.
With financials high on the takeover scale, blue chip banks enjoyed heady support. Royal Bank of Scotland, up 61p at 931p, led the pack with some prepared to bank it will feature in a financial deal.
Standard Chartered was another in the bid frame. The shares gained 38p to 673p, building on last week's flurry, when heavy buying was apparent. Standard has had a poor run since the Asian crisis developed. The shares have come down from a 1,081.5p peak hit last summer. The theory abounds that a predator plans to take advantage of the under-performance.
Other financials buoyed by bid hopes included General Accident and Norwich Union. Barclays, despite a bigger than expected pounds 340m loss on BZW, managed a 41p gain to 1,886p, a peak.
But Halifax and Woolwich, which have been strong on speculative buying, had, for them, rather quiet sessions with Halifax up 6p at 899p and Woolwich 3p at 388p.
Telecoms, another area where mega-mergers are expected, featured Cable & Wireless with a 37p advance to 619p and BT, the subject of frenzied buying two weeks ago on corporate stories, up 9.5p to 594.5p.
Rolls-Royce, one of the overseas earners weighed down by sterling's strength and the turmoil in the tiger markets, climbed 6.5p to 213.5p on hopes that the 29.5 per cent ceiling on foreign shareholdings is about to be lifted. British Aerospace, which endures a similar ownership restriction, rose 10p to 1,600p. BAe scored from the Government's decision to pump pounds 123m towards the design and development of a new range of Airbus Industrie airliners.
The ceiling, which has caused particular discomfort to Rolls, with foreigners forced to sell shares, is expected to be raised to 49.9 per cent or perhaps abolished altogether.
Micro Focus, the computer group, hardened 157.5p to 2,895p on reports of a deal with Microsoft.
Bass, down 26p to 944p, and Ladbroke, off 6p to 290p, were hit by second thoughts about a costly bid battle for InterContinental Hotels. BSkyB, interim figures today, lost 19.5p to 342p. Profits are expected by up to pounds 9m lower at around pounds 125m and the market is anxious about possible delays in the digital television roll-out.
Gibbs Mew, once a brewer, now a pub owner, jumped 52p to 30.8.5p on signalled bid talks; pubs chain JD Wetherspoon lost 15p to 277.5p on profit downgradings.
Retailer La Senza added 8.5p to 25.5p on discussions with ``a number of parties". Tele-Cine Cell, on a bid approach, gained 4.5p to 61p.
Phytopharm continued to draw strength on licence hopes for its drugs- from-plants.