Squire Patton Boggs London managing partner Robert Weekes is stepping down as head of the City base, with the firm's global managing partner Stephen Mahon relocating to London to take over leadership of the office.

Mahon, who is moving from Cincinnati to take up the role, will retain his position as global managing partner for clients and strategy while assuming Weekes' responsibilities at the helm of the London base.

Weekes, who has been London managing partner for 10 years, will remain with the firm as a fraud partner in London.

Mahon, who is also a member of Squire Patton Boggs' executive leadership group, has held other senior management roles at the firm, including global business practice leader and chair of the firm's private equity practice group.

Squire Patton Boggs chairman and global CEO Mark Ruehlmann commented: "I could not be more grateful to Robert for his leadership of one of our firm's largest and most important offices. Steve is respected among our partners across our 47 offices and, as our global managing partner, will continue to build on the success the London office has achieved."

In 2016, Squire Patton Boggs saw revenues grow 6% to $983m, while profits per partner jumped 15% to $975,000. The US-based firm – which has a significant UK presence due to its 2011 takeover of Hammonds – is yet to post its financial results for 2017.

The firm has recently made headlines for its work for under-fire political consultancy Cambridge Analytica, which it is advising on the Information Commissioner's Office investigation into the company's use of Facebook data for US President Donald Trump's election campaign.

It is also currently attracting much media attention for its links to Trump's personal lawyer Michael Cohen, whose office in New York's Rockefeller Center – which he had shared with Squire Patton Boggs – was raided by the FBI last week.

Cohen, who is under investigation by Manhattan federal prosecutors, was given the office as part of an alliance with Squire Patton Boggs, which was formed in April last year. He was paid a $500,000 (£350,000) annual "strategic alliance fee", by the firm and would also receive a percentage of the fees charged by Squire Patton Boggs for clients introduced to it by Cohen under certain circumstances, according to prosecutors.

In court papers, prosecutors said Cohen's claim that he has confidential communications with multiple clients is exaggerated, as Cohen has told at least one witness that he has only one client – President Donald Trump.

Cohen has also claimed to have privileged communications though Squire Patton Boggs. At the time of the alliance, the US firm announced that Cohen would help "advance the interests" of the firm's clients and work with its lineup of lobbyists. Squire Patton Boggs is unnamed in prosecutors' briefs, but the firm announced on 9 April – the same day as Cohen's office was raided – that their alliance had been terminated.

The alliance agreement also spelled out other aspects of the relationship between Cohen and Squire Patton Boggs, including that Cohen would be given an office at the firm; Cohen would maintain his own computer server system not connected to the firm's computer server system; and the firm would not have a key to Cohen's office.

For the duration of the agreement, Cohen introduced five clients to Squire Patton Boggs, prosecutors said. Cohen did not maintain timesheets at the firm and Cohen did not bill any clients through the firm, prosecutors said, adding that Squire Patton Boggs is not aware one way or another whether Cohen billed any of the clients for services of any kind.

A spokesman for Squire Patton Boggs declined to comment on the total amount of money that the firm paid to Cohen during the course of its alliance. The spokesman said Squire Patton Boggs could confirm what prosecutors said in their Friday brief: "That Michael Cohen was never an employee or partner of our firm."

Additional reporting by Christine Simmons.