CMS Cameron McKenna has won the lead role for Royal Mail on its largest transaction since cutting down its legal panel to just three firms at the end of last year.

The UK top 15 law firm advised Royal Mail on an agreement to extend its facilities management contract with joint venture (JV) company Romec for a further 10 years, with the deal worth up to £1.8bn.

Romec, which is 51% owned by Royal Mail and 49% owned by Balfour Beatty, will provide contracted services such as electrical, plumbing, security and cleaning to Royal Mail Group, with the deal initially worth £900m, with scope for further services worth an additional £900m.

The deal also saw Balfour Beatty buy the JV's subsidiary responsible for providing external facilities management services, Romec Services Limited, for an undisclosed amount – with Romec now to focus on Royal Mail.

Camerons' team was led by Royal Mail corporate relationship partner David Day, supported by construction partner Karen Clarke.

Meanwhile, Berwin Leighton Paisner (BLP) took the lead role for Balfour Beatty, running a team including corporate finance partners Rob Salter, Simon Pollock and Adam Bogdanor, commercial partner Richard Shaw and tax partner Gary Richards.

McGrigors also advised Romec, with a team led by Manchester corporate and commercial partner Nick Ogden.

Day commented: "This deal had a very strong corporate element and outsourcing focus, which fits in with the kind of work we have done for Royal Mail previously. We have quite a strong pipeline of work from Royal Mail and are very pleased with how the relationship is working for us at the moment."

Camerons was one of three firms appointed to Royal Mail's panel in December last year, alongside Beachcroft and Bond Pearce. The company continues to instruct Slaughter and May for its City work, which was not part of the review.