Visitors may have to start paying to visit Belsize Park’s Isokon Gallery after it was hit by a drop of up to £10,000 in revenue during the coronavirus pandemic.

The museum in Lawn Road had to close its doors and cancel guest lectures, tours, and an exhibition when lockdown hit on March 23.

It has been boosted by a £3,000 grant from Historic England, and attendees at planned guest lectures chose to forego refunds on cancelled events. But when it closed, the finances were already dented after spending thousands on upgrading a 15-year-old boiler and out-dated fuseboard.

The trust that runs the gallery has had to pay rent to the Notting Hill Housing Trust during the four-month closure, along with heating, and insurance, all while having no income from visitors.

While Magnus Englund, a director of the trust, said closing the gallery was not under consideration, he added that if a crowdfunder doesn’t raise £8,000, it may have to start charging visitors.

He said: “With the museum, the important thing for all of us is for as many people as possible to see it, and hear its story. If we have to charge then it would lose visitors. We don’t want that to happen at all.

“It being free is holy to us. We really don’t want to charge anyone. We want this to be open to as many people as possible, for free, like many of the big museums in central London.”

The cause is one close to Mr Englund’s heart, as the 53-year-old lived in the 1930s’ block’s penthouse for five years until 2018.

“It’s a little bit unexpected when you’re surrounded with all these red brick buildings. It’s a one-off, the first re enforced concrete block of flats in Britain, and you had this amazing network of people living here,” he said.

The Isokon, which was opened in 1934, is one of the key examples of modernist architecture in Britain. It took its name from the architects firm that specialised in building modernist houses, flats, furniture and fittings. The block played home to some of the most influential thinkers, architects and artists in north London, including the Bauhaus designers Walter Gropius, Marcel Breuer and László Moholy-Nagy.

Agatha Christie, the subject of an exhibition next year, lived there for six years during the Second World War. Research ahead of the show found that she wrote Mousetrap, the West End’s longest running play, while living in Belsize Park.

When it closed earlier this year, a show about former Isokon residents Jacques Groag, an architect and furniture designer, and his wife Jacqueline, a textile and pattern designer, had just started. The couple moved to Britain on the eve of the Second World War to live as Jewish émigrés.

Jacqueline went on to have success in Britain as a fabric designer, with one of her designs being worn by the Queen.

The museum reopened for the first time since lockdown on July 17. Visitors now have to wear a mask, use hand sanitiser and work their way clockwise around the inside. There are hopes that an extended opening this year, until December, may allow visitors to make up for lost time during the spring.