In heavy trading - the Seaq system put turnover at 47 million shares - BTR plunged 44p to 338p, with at least one US securities house telling clients the price was heading for 290p.
The once top-performing company produced interim figures that created a clutch of worries about its ability to enjoy the benefits of an improving world economy.
Year's profit forecasts were pulled back across the board with analysts coming down from about pounds 1.44bn to pounds 1.3bn.
Alan Jackson, BTR chief executive, was suitably baffled. 'We don't understand it; the City has misunderstood us; I think they are an excellent set of results.'
It was not only BTR shares that were savaged: the five traded warrants were devastated. The 1993/94 issue, giving the right to buy shares at 288p, not surprisingly nearly halved to 45p; the 1994/95, with a 222p price, fell 45p to 112p. The most recent issue, giving the right to shares at 405p in 1998, lost 17p to 53p.
The BTR display tended to crystallise market suspicions that profits in the present results season will be below expectations. Disappointment has been expressed with many of the blue- chip performances, and with worries about interest rate increases never far below the surface some commentators are wondering whether shares are due for a sharp correction.
Among others to produce figures, Blue Circle Industries fell 14p to 300p; Cadbury Schweppes 4p to 468p; and Glaxo 3p to 609p. Arjo Wiggins Appleton, the Anglo-French packaging group, bucked the trend, up 8p to 287p; so did Enterprise Oil with a 13p gain to 400p.
But BTR, with help from the futures market, pulled the FT-SE 100 index 23.9 points lower to 3,180. At one time it was down 37.7. A firm New York opening helped to trim losses.
The market also had to contend with an aborted sell programme. What one trader described as an 'idiotically handled' exercise put market- makers on edge and in no mood for the wave of selling that greeted the BTR results. The sharp reduction in Britain's world trade deficit had little, if any, impact.
Government stocks edged higher as a Confederation of British Industry survey indicated a cooling in retail sales, easing interest rate pressure.
Building and related shares were knocked back. BCI, despite a 27.8 per cent gain in operating profits, failed to offer any support. Results from the builder John Laing were also poorly received with the shares down 21p to 269p. It was, however, the Halifax Building Society's gloom on house prices that did much of the damage.
Associated British Foods bucked the trend, helped, it was thought, by positive noises from Panmure Gordon. The shares rose 10p to 564p.
United Biscuits, where takeover hopes continue to hover, was another to move ahead, despite sell advice from Williams de Broe. Interim results are due next week and Williams analyst David Hallam is looking for pounds 76m, up 7 per cent. For the year it expects pounds 188m against pounds 162.3m.
Zeneca, the drugs group, was another to shrug off the gloom, up 16p at 838p. A facility to raise cash in the US helped sentiment; so did James Capel comments that it was its favoured drug share.
Wellcome was supported by its potential rival to Imigran, the Glaxo migraine treatment, improving 13p to 696p.
The latest outbreak of hostilities in the mobile telephone market left Cable and Wireless 9p down at 430p and Vodafone, in heavy trading, off 3p at 202.5p.
Whitbread suffered on the beer pitch, retreating 11.5p to 550.5p. The shares have been strong lately, prompting Nomura to suggest a switch into Scottish & Newcastle, down 2p at 519p.
The publisher Emap's pounds 77.2m cash call left the shares 3.5p down at 414.5p; Flextech jumped 15p to 459p on its proposed television business channel with the US Dow Jones organisation.
Litho Supplies tumbled 29p to 197p after a warning that year's profits would show only a minimal improvement.
Orb Estates achieved the somewhat dubious distinction of scoring the day's best gain, a 33 per cent advance to just 1p. The company used to be called Ossory Estates before a revamping exercise.
The FT-SE 100 index fell 23.9 points to 3,180. At one time it was down 37.7. The supporting FT-SE 250 index gave up 17.3 to 3,761.8. Turnover was 668.5 million shares with 27,450 bargains. Government stocks were firm.
Gowrings continues to develop its Burger King operations. It has 16 outlets and expects to reach 30 in two years. In the half-year to June leisure operations made trading profits of pounds 280,000, exceeding the traditional motor side's pounds 154,000. Half-year profit came out at pounds 179,000 (a pounds 137,000 loss). Peel Hunt expect year's profits of pounds 650,000 against pounds 54,000. The shares rose 3p to 78p.
Hampden, the Belfast-based do- it-yourself retailer, gained 4p to 30p, reflecting hopes of an IRA peace dividend. The shares have risen from 23p this week. The group, where Ladbroke has 29.9 per cent, has an erratic trading record, slumping into a pounds 220,000 loss last year. At one time profits nudged pounds 1.5m. Its shares arrived at 57p nine years ago and hit a 118p peak in 1987.Reuse content