A Swedish pension fund is due to decide next week whether to support the deal. It has around 4 per cent of the Astra capital.
If it should come out against the merger, there are worries that, with Astra's small shareholders, a blocking vote could materialise, as Zeneca needs at least 90 per cent of the capital to win the day.
Sources close to Zeneca believe such an event is highlyunlikely. It is pointed out that the pension fund invariably follows the wishes of a company's employees and the Astra workforce is in favour of the merger.
The fund was supportive of an earlier big drugs get together, the American- Swedish alliance which resulted in Pharmacia & Upjohn. It has come out against major deals - Renault and Volvo was one - but then the car workers were far from happy about the suggested merger.
It is thought many small Astra shareholders will accept the terms, although their lobbying organisation is against it.
The giant merger is due to be completed next month and despite the scare stories from Sweden is expected to go through. The two companies have seen more than 150 institutional investors in the past few weeks and it is thought they received encouraging responses.
In a letter to its shareholders, which could indicate some anxiety about their attitude, Astra said the Zeneca deal was the best way forward and could unlock the US market for its drugs.
Stephen Ewing at WestLB Panmure said Astra shareholders "would be mad" not to accept the deal. Zeneca shares firmed 17p to 2,629p in busy trading.
The rest of the market failed to hold best levels. At one time, on the back of the overnight Wall Street surge, Footsie was up 115 points to 6,185.2, just 10.4 below its trading peak. It closed 85.3 higher at 6,155.2, only 23.8 below the all-time high, hit last July.
Results also helped the early progress. National Westminster Bank was at one time up 104p but had to settle for a 45p gain at 1,319p. Unilever, on its pounds 5bn handout, was treated even more harshly. At one time up 33p, it ended 1p lower at 624.5p as some cash-rich institutions wondered whether they really wanted yet another cash injection.
Railtrack, ahead of tomorrow's railway summit, reversed a further 29p to 1,403p.
Corporate action was again a major influence. BSkyB rose 18.25p (after 31.5p) to 536.75p on the possibility of a link, perhaps even a merger, with Canal+, the French pay-TV group.
Coutts Consulting, where bid talks were confirmed, rose 7p to 35.5p and BS, the old Bristol Stadium, raced ahead 25p to 145p after reporting bid negotiations were taking place.
Allied Leisure, up 2p to 27.5p, and European Leisure, 1.5p at 70p, at last admitted talking merger - stories of a deal were circulating last month - and printer Wace inked in a 5p gain to 76p as Allied Graphics, a US group, said it might counter an agreed offer from another American business, Schwak. The bidding war started when Photobition made an offer which Schwak topped with a pounds 94.6m shot.
Kenwood Appliances rose 5p to 99p as speculators prowled, with some aggressive funds increasing their holdings, and blistered sausage-skin group Devro climbed away from its 12-month low, up 18.5p to 163p, with a little help from the boys in dark glasses.
Arm, the chip maker that came to market nearly a year ago, rose a further 55p to a 2,040p peak following an investment lunch hosted by ABN Amro. Acorn, the computer group nursing a big Arm stake which it plans to sell, firmed 5p to 163.5p.
Ladbroke, up 1.75p to 272p, was also helped on its way by ABN, and Vodafone improved 33p to 1,172p as Merrill Lynch lifted its profits expectations.
Gallaher was puffed 3.5p higher to 423p with BT Alex.Brown hanging a buy sign on the shares.
On the under-card, Drew Scientific improved 21p to 97.5p after it obtained the approval of the American Food and Drug Administration for a heart disease test.
NXT, the maker of flat panel loudspeakers, jumped 52.5p to 481.5p in busy trading, after saying it had signed 24 new licensees in the past four months. The group, the old Verity, says it has developed a new transparent, wafer-thin speaker.
Easynet climbed 26p to 261p after linking with Eidos, the computer games group, to provide an Internet service caused Eidosnet.
Profits warnings lowered Total Office 14p to 38.5p and Oxford Asymmetry showed once again that the market is not prepared to take prisoners when its forecast profits failed to impress. The highly rated shares lost 59p to 499p.
SEAQ VOLUME: 922.5 million
SEAQ TRADES: 82,222
GILTS INDEX: n/a
CALLUNA, the computer group, was the most actively traded under- card share, with Seaq putting volume 9.7 million as the price fell 4p to 23p. After the close came the reason; year's results will be "substantially below" market expectations and there was a hint that a cash call was being considered. The group, which has a computer security system, hit 38.5p last summer and has been 96p.
SHARES OF Waterfall, the bars and snooker clubs chain, held at 59p with little investment interest apparent. Yet it could soon be engulfed in bid action if the confirmed Allied Leisure/European Leisure talks produce a merger. EuroLeisure has a hostile 23 per cent stake in Waterfall, which last year had abortive merger talks with the Springwood leisure group. Waterfall touched 108p last year.