Brexit has exposed the weakness of the UK economy.
The GBP has long been over-valued.
Financial experts have been quoted as saying the UK produces less than it consumes and pays for that by borrowing from foreigners.
Last century the GBP was worth as much as 5 x USD. Now its a paltry 1 x and falling.
The UK economy is devasted since Brexit and the GBP has been declining since the end of the North Sea oil and gas boom.
Being designated the "worst performing economy in the OECD" doesn't help.
"To Mr. Goldin, the pound’s journey indicates a decline in economic and political influence that accelerated when Britain voted to leave the European Union in 2016. In many respects, Britain already has the worst performing economy, aside from Russia, of the 38-member Organization for Economic Cooperation and Development.
https://www.nytimes.com/2022/09/28/business/economy/uk-pound-history.html
“It’s just a question of time before it falls out of the top 10 economies in the world,” Mr. Goldin said. Britain ranks sixth, having been surpassed by India.
Eswar Prasad, an economist at Cornell University, said this latest plunge had delivered a bracing blow to Britain’s standing. A series of “self-inflicted wounds,” including Brexit and the government’s latest spending plan, have accelerated the pound’s slide and further endangered London’s status as a global financial center. "