The high-profile British player in the eVTOL market is Vertical Aerospace. The Bristol-based company was founded in 2016 by businessman Stephen Fitzpatrick, who also set up OVO Energy.

Its striking VX4 design uses eight large propellers mounted on slim, aircraft style wings to generate lift. Mr Fitzpatrick has made ambitious claims about the aircraft, suggesting it would be “100 times” safer and quieter than a helicopter, for 20% of the cost.

The company has made progress. After completing a programme of remote-controlled testing, it began carrying out piloted tests earlier this year. Initially, these were carried out with the aircraft tethered to the ground. In early November, it carried out its first untethered take-off and landing.

But there have also been serious setbacks. In August last year, a remotely-piloted prototype was badly damaged when it crashed during testing at Cotswold Airport, after a propeller blade fell off.

In May one of its key partners, the engineering giant Rolls Royce pulled out of a deal, external to supply electric motors for the aircraft.

Ambitions remain sky high. Vertical Aerospace says it will deliver 150 aircraft to its customers by the end of the decade. By then, it also expects to be capable of producing 200 units a year, and to be breaking even in cash terms.

Yet financial strains have been intensifying. Mr Fitzpatrick invested an extra $25m into the company in March. But a further $25m, due in August if alternative investment could not be found, has not been paid. As of September, Vertical had $57.4m on hand – but it expects to burn through nearly double that over the coming year.

Hopes for the future appear to be pinned on doing a deal with the American financier Jason Mudrick, who is already a major creditor through his firm Mudrick Capital Management.

He has offered to invest $75m into the business – and has warned the board of Vertical that rejecting his plan would inevitably lead to insolvency proceedings. But the move has been resisted by Mr Fitzpatrick, who would lose control of the company he founded.

Sources close to the talks insist an agreement is now very close. The company believes if a deal can be done, it will unlock further fundraising opportunities.