Several dealers said CSFB appeared to be behind the transaction after it placed 55 million Corus shares last week as part of a deal whereby Russian tycoon Alisher Usmanov locked in profit from his Corus stake. CSFB, which said earlier this week it held 15.3 percent of Corus' shares, declined to comment.
The FTSE 100 share index closed down 0.2 points at 5,057.2, to leave the index up 0.3 percent on the week and up over 4 percent since the start of the month.
Dealers said renewed talk that Barclays could be on the radar of a rival US bank also provided some interest on a subdued day and helped its shares add 0.9 percent, but most dismissed the talk and noted recent take-over candidates Gallaher, Sainsbury and SSL all lost ground as speculation on moves for them faded.
Dealers said activity was subdued due to a lack of corporate news, the last day of UK school holidays and slowing trade on Wall Street ahead of a holiday there on Monday.
A bigger-than-expected jump in US producer prices raised the threat of a rise in US interest rates, which some analysts said equities investors appeared to be ignoring.
"We think it's skating on thin ice," said Steve Russell, head of research at Ruffer Investment Management.
He said he expected a market pullback but the timing was uncertain as UK equities had been well supported by inflows from institutions and from overseas. "But we think the foundations of the move of the last couple of months aren't solid enough," he added.
Cairn shares rose 4.4 percent to take their two-day rise to 11 percent since it gave a reassuring update on its drilling operations in India, prompting Dutch bank ABN Amro to upgrade its rating on the stock to "buy" from "add". The more upbeat mood spilled over to mid-cap rival Burren Energy, up 6.5 percent.
But fixed-line telecoms firm BT shed 2.3 percent, trimming gains since it posted robust earnings growth last week, and airline British Airways also succumbed to selling pressure as dealers said confidence in the health of economic recovery may have been overdone.
Scottish & Newcastle climbed 2 percent on optimism for robust results next Wednesday after its half-owned Eastern European brewer, BBH, reported strong Russian beer sales and a bullish outlook for further growth earlier this week.
But cigarette maker Gallaher slipped 0.9 percent after long-mooted predator Japan Tobacco made no mention of potential acquisitions, dealers said. Speculation that Japan Tobacco is mulling a take-over of the firm has swirled for months.
Fading take-over hopes also knocked midcap SSL International 2.7 percent lower. ABN said shares in the maker of products from Durex condoms to Scholl footwear had been bloated by take-over speculation.
"Although in theory there are several potential bidders, it is unclear whether SSL's brands have the required scale to attract the large consumer goods manufacturers, and the absence of the rights to Scholl in the US may dissuade many of the multi-national players," the Dutch bank said, taking a "reduce" stance on the company.