Markel International is looking to write £20m GWP in employment practices liability (EPL) business through its new regional offices.
The move is part of the insurer's plans to double the size of its UK regional business, Markel UK.
Jeremy Brazil, Markel International director of London underwriting, said: "We are keen to promote EPL. We write $40m GWP (£23m) in the US and we should be able to repeat that in the UK through our new regional offices."
Markel UK will open an office in Cambridge this month, one in Edinburgh in August and a third regional office in Bristol in September.
Twelve underwriters will be recruited and divided among the new offices.
The company also plans to make its London base the flagship office of the global company.
Brazil said the London office would become a platform for writing international business as it expanded its regional presence.
"This year marks Markel's 75th anniversary and its fifth year in London.
"We will also be opening offices in Canada and Madrid this year and we hope for London to become the platform for international business."
In January, Markel Corporation president and chief executive Tony Markel pledged to invest $50m capital into its London operations.