Gibson Dunn and Slaughter and May have won lead roles on Hewlett-Packard's (HP) £7.1bn takeover bid for Britain's largest software company Autonomy, in a deal which could become the largest ever in the history of the European IT sector.

Gibson Dunn was instructed by the US IT giant as lead counsel in both the UK and US, with magic circle firm Freshfields Bruckhaus Deringer brought in as co-counsel, taking a supporting role on corporate matters and providing competition and employment advice.

Gibson Dunn fielded a cross-border team led in London by corporate partner Jeffery Roberts, who worked alongside fellow corporate partner Selina Sagayam and finance partner Gregory Campbell. The firm's New York team was led by corporate partner Dennis Friedman.

Freshfields' team was headed by London corporate partners Ben Spiers and Ed Braham, with Nick Squire and Tom Ensign taking the lead on employment and antitrust matters respectively.

US law firm Drinker Biddle was also instructed by HP, providing antitrust advice through a team led by Washington DC-based competition partner Bob Skital.

HP's board of directors meanwhile took advice from a London-based team at Skadden Arps Slate Meagher & Flom.

Slaughters took the lead role for Autonomy, with London corporate partners Steve Cooke and Gary Eaborn at the helm.

US firm Morgan Lewis & Bockius, meanwhile, provided the FTSE 100 company with antitrust advice, running a team led by New York antitrust partner Harry Robin.

The offer, which has been accepted by Autonomy's board, values Autonomy at a premium of around 64% compared with its market value on Tuesday (17 August).

The bid has already provoked political concerns about the overseas takeover of another UK company.