you can pay cash to take a bus and ferry to the UK, but how do you pay the travel authorisation fee (£16)?

And I suppose the same question can be asked of the US and EU, who also impose a surcharge on inbound travelers who are subject to travel authorisations.

(yes, there is a bus from London to New York if anyone is wondering; and indeed there would potentially be many travel authorisations to pay for along that route depending on how many governments are doing this)