Guess the black cab ride price.

So tonight was flying in from Geneva to London city, but flight was cancelled and I was sent to Heathrow instead.

BA customer service told me to get a black cab home and claim it back.

So:
830pm from T5 Heathrow to Orpington (about 45 miles)
No traffic
Didn't stop once.

Guess how much it cost in a black cab?

(Would have taken an uber but was an hour's wait)