Slaughter and May is being thrown into the fray to defend Blue Circle against a hostile takeover bid from French firm Lafarge.
Blue Circle is fighting off a £3.4bn debt and equity bid from the buildings materials business, which the UK cement maker has condemned as "unsolicited and unwelcome".
William Underhill, corporate partner at Slaughters, who is heading a team of five lawyers at the firm, says: "In these situations there is no time for preparation and the response must be made quickly but accurately."
Underhill's team includes highly-rated competition partner William Sibree, corporate partner Jeff Twentyman, corporate assistant Tim Parker and competition assistant Marc Israel.
The team is likely to increase in numbers as Underhill says the firm's Paris office will become involved.
It is believed that Linklaters & Alliance's Paris office is acting for Lafarge, but the firm was unavailable for comment.
Lafarge's offer for Blue Circle is the first major hostile takeover attempt this year.
It follows a spate of bold bids last year, including Slaughters' client Punch Taverns snatching Allied Domecq's retail arm from under the nose of Whitbread.
Underhill says: "My personal view is we will continue to see the same sort of thing we saw last year. From a lawyer's point of view it is happening for market reasons."
Richard Tapp, company secretary and legal adviser at Blue Circle, says the entire in-house team is embroiled in defending the company against Lafarge's intentions.
However it is unclear how Blue Circle intends to fight off the hostile bid.
It is believed the company will either attempt to consolidate by making an acquisition itself, or seek a "white knight" to bail it out.
This is the third major deal Slaughters has acted on for Blue Circle since July last year when it advised the company on selling off its heating and boiler divisions.