Simpson Thacher & Bartlett has taken a lead corporate role for Pennsylvania Power and Light (PPL) on its £4bn acquisition of E.ON's UK power networks following a competitive auction.

The US law firm was instructed less than six weeks ago, and fielded a team led by London corporate partner Adam Signy (pictured). Other partners to act on the deal included New York capital markets head Vince Pagano and fellow corporate partner James Cross.

Allen & Overy and Ashurst also advised the US acquirer in support of Simpson Thacher. At A&O, corporate partner Eileen Kelliher led, assisted by corporate partner Richard Evans. Ashurst, meanwhile, advised on competition and regulatory issues with a team led by senior economist Mat Hughes.

The PPL bid trumped what had been regarded as a winning bid from Cheung Kong Infrastructure (CKI), the investment vehicle of Hong Kong billionaire Li Ka-shing. CKI instructed a London-based team at CMS Cameron McKenna led by corporate partner Charles Currier.

CKI last summer instructed DLA Piper when the investment company carried out a £5.6bn acquisition of EDF's UK electricity networks.

Linklaters, meanwhile, is advising the vendor, German utility company E.ON. London corporate partner Matthew Middleditch is leading a team including fellow corporate partner Roger Barron and managing associate David Martin.

E.ON had been in discussions with a number of potential investors in relation to the disposal, including Canada Pension Plan Investment Board and Abu Dhabi Investment Authority, which pulled out of the process in January.

E.ON put its UK networks up for sale in December as part of a pledge to investors that it would divest assets of up to $21bn (£13.2bn) in the coming three years.