Hotel and leisure group Principal Hayley have vowed to create a luxury landmark hotel inside the historic Liverpool bank building used to hide most of Britain’s gold reserves during the Second World War.

The developers will spend £50m (US$71.5m, €64.5m) to transform the interiors of the Grade II listed neoclassical Martins Bank building into a five-star 227-room hotel, spa, bar and fine dining destination.

Full planning and listing has already been granted and construction will start on the project this year, with a potential opening in late 2017 or early 2018. The design team working on the conversion has not yet been revealed.

Tony Troy, CEO of the Principal Hayley Group, said the hotel will give the company an important presence in the heart of Liverpool, where there is currently no full service luxury hotel for leisure visitors.

He said: “Our development will become the jewel in the crown of Liverpool’s hotel offerings and we’ll be working very closely with heritage experts to ensure our conversion of the building is sympathetic to its unique historic and architectural features.”

Castlewood Securities, which has owned the Martins Bank building for 20 years, has been acquired by Principal Hayley Group Hotels in the deal.

“I’m pleased to see these new and ambitious plans for bringing another iconic Liverpool building back into use” said the city’s mayor, Joe Anderson. “It is an important landmark in the city’s business district and its conversion to a destination hotel reflects the continuing strength of the city’s visitor economy.”

The Martins Bank building – which opened in 1932 – was designed by Liverpudlian architect Herbert Rowse and is widely considered one of his most iconic works.

At the start of World War II, when fears of a Nazi invasion were at their height, the majority of Britain’s gold was transported to Liverpool in three heavily guarded trains and transferred to the bank’s vaults. The mission was dramatised in the 1993 Emmy-winning film The Bullion Boys.