Willkie Farr & Gallagher boosted London revenues by almost 50% during 2017, a year in which the US firm posted record results across all key financial metrics.

The City office generated $53m (£38m) in revenue over the calendar year, up 47% from $36m (£26m) in 2016, the firm said. The London base has more than 50 lawyers focused on compliance and enforcement, insurance, asset management, restructuring, private equity and competition.

Recent high-profile mandates have included advising Barclays on fraud charges brought by the Serious Fraud Office relating to the bank's capital raising arrangements with Qatari investors during the 2008 financial crisis.

The firm also recently bolstered its London partnership ranks with the hire of Slaughter and May associate Simon Osborn-King, who is joining as a partner after more than 10 years at the magic circle firm.

Firmwide revenues rose nearly 12% to $772m (£548m) during 2017, while profit per equity partner rose 13% to $2.97m (£2.1m) and revenue per lawyer (RPL) rose 5% to $1.2m (£852,000), according to preliminary ALM reporting.

The firm increased its profitability even as it boosted its size, with total lawyer headcount rising 6% to 644 lawyers. The firm's equity partnership ranks increased by three to 145.

Gartner said private equity and M&A work were key drivers of the growth, but litigation, restructuring and asset management were also "big contributors." As well as London, he said there was substantial contributions from the firm's Frankfurt and Paris offices.

Fresh off the record results, Willkie Farr has added a string of partners in the first quarter of 2017.

In addition to the London hire of Osborn-King, the latest recruits include Vinson & Elkins fund formation practice leader Mark Proctor; New York tax partner Russell Pinilis, who joined from KPMG in early March; and Houston-based energy transactions lawyer Steven Torello, who moved over from DLA Piper in February.

"When you have tremendous financial success," said Willkie co-chairman Steven Gartner, "you become a more attractive venue." Gartner added Willkie is on the radar of more laterals and has seen more inquiries about potential moves.

While sharp billing rate increases are a strong driver of revenue growth for many New York firms, Gartner said Willkie's rate increases were "a small part" of the revenue rise, as the firm saw total hours billed increase.

Co-chairman Tom Cerabino said in a statement that the firm had a very busy fourth quarter, "which bodes reasonably well for 2018."

In 2017, Willkie represented private equity clients including Aquiline Capital Partners, Centerbridge Partners, FFL Partners, Genstar Capital, Insight Venture Partners, The Sterling Group, Warburg Pincus, Ardian, IK Investment Partners and PAI Partners in many transactions.

Willkie's M&A team advised internet provider Level 3 Communications when it was acquired for $34bn by telecoms company CenturyLink, while the firm's restructuring group represented Brookfield Business Partners in its pending acquisition of Westinghouse Electric, the bankrupt nuclear services company, for $4.6bn.