Mace has paused work at Hanover Square in west London while Lendlease has also suspended construction at Oxford House.

Work is continuing at The Hickman development in east London by Ellmer Construction.

In a trading update to the city this morning, the developer said: “Whilst activities currently continue onsite at The Hickman, E1, our contractors have temporarily suspended activities at our Hanover Square, W1 and Oxford House, W1 development sites while they consider how they can continue to work within Government guidelines.

“We are also maintaining our regular payments to suppliers to ensure their cash flow is maintained given the challenging economic backdrop.”

Many public clients have been ordered to keep payments flowing to the construction supply chain.

But the industry fear is that private clients will take a much tougher line with any work delays.

One contractor said: “At least there is a party line with public clients and we should hopefully see them sticking to that.

“It’s a much greyer area on the private side and there’s no guidance coming down from the industry trade bodies over what they’d like to see private clients do.

“Some will do the decent thing but the fear for a lot of main contractors is that private clients will put the squeeze on us during this crisis and after in terms of claims for any delays.”

Great Portland estates chief executive Toby Courtauld said: “Despite these unprecedented conditions, the GPE team is pulling together well, focussing on our top priorities of the safety and wellbeing of our occupiers, suppliers and employees and ensuring that our portfolio is as prepared as can be for a potentially prolonged period of lockdown.

“However long the Coronavirus lasts, with our low gearing and ample liquidity, GPE is well positioned to weather the impact until market conditions normalise.”