Ten Trinity Square, one of the insurance industry's most impressive buildings, may be sold by its owners Willis, after new chief executive Joe Plumeri said he wanted his London workforce under one roof.

Willis was tight-lipped about the building's future, but admitted that there was no room in either the Ten Trinity Square headquarters nor in the company's Camomile Street offices to house the entire 1,300 staff in the capital.

Nick Jones, director of group communications at Willis, said that there were about 800 staff in Trinity Square and 500 in Camomile Street. There was insufficient room for one office to absorb the other.

“Joe wants to have all the people under one roof and it is one of his clear, explicit objectives,” Jones said. “What is the point of having everyone scattered around London when you want to establish a one-company culture?”

The Trinity Square office, near the Tower of London, was originally the Port of London Authority's headquarters. It was designed

by Sir Edwin Cooper and opened by prime minister David Lloyd George in 1922.

One London property consultant estimated that the Grade B listed building could be worth up to £100m. Willis took over the freehold of the 24,000sqft building in 1974, according to Estates Gazette Interactive.

Although it was bombed during the Second World War, most of its original features survived.

In what has to be a case of bad luck repeating itself, the concrete and glass Camomile Street office was also bombed – this time in the IRA attack on the City in 1993.

Willis was already a tenant, having taken over 70,000sqft, on floors three to eight, in 1981. This lease will expire in January 2006.

Jones said there was no timetable for the move and could not say whether the search for a new building was under way.

Plumeri became chairman and chief executive of the broker giant in November, after 32 years at Citigroup.

Willis has 235 offices in 73 countries. It handles gross premiums of £9bn a year.