The Co-operative Group has followed its conversion to an alternative business structure (ABS) with a transformative £750m acquisition of 632 Lloyds TSB and Cheltenham & Gloucester bank branches.

The Co-op, which instructed magic circle firm Clifford Chance (CC) on the acquisition last year, will pay £350m upfront and an additional £400m based on the performance of the combined business.

CC, which has a longstanding corporate relationship with the bank, fielded a team under London corporate partners Hilary Evenett, Mark Poulton and Andre Duminy. London antitrust head Alex Nourry is the firm's Co-op relationship partner.

Lloyds' sale of the branches, which was demanded by European regulators after Lloyds was part-nationalised in 2009, was overseen by a Linklaters team headed up by global relationship partner Jeremy Parr alongside corporate partner Matthew Bland and capital markets partners Carson Welsh.

The deal will take the Co-op's total number of branches to almost 1,000, increasing its personal current account market share to almost 7%. The move has been hailed as a transformative one for Co-op, with BBC business editor Robert Peston describing it as "the deal of the millennium".

The acquisition comes after the Co-op recently confirmed its intention to roll out its legal services offering to all of its existing 330 high street outlets following a successful pilot of the scheme last year. However, a Co-op spokesperson said that it was too early to tell whether legal services would be made available at all of the 632 new branches.

The Co-op was this March confirmed as one of the first three ABSs to be licensed by the Solicitors Regulation Authority, with its legal arm now set to offer services previously reserved for solicitors.

Confirmation of the deal comes almost a year after the bidding battle for the Lloyds branches began, with NBNK – a banking venture set up in 2010 by Lord Levene, the chairman of insurer Lloyd's of London – submitting a £1.5bn offer in October. NBNK was advised on its unsuccessful bid by Slaughter and May.