But even so...
O'Dwyer is a bad example, but even so, he should not be liable for extradition:
"For the UK to agree to extradition, a person must be accused of "an offence under the law of the relevant part of the United Kingdom punishable with imprisonment for a term of 12 months or a greater punishment”."
So, the arrangement at present is that to be extradited, someone must have committed a crime in the UK? So why can't they be tried and punished (if convicted) in the UK? If foreign governments have evidence then that can be presented and tested through cross-examination in a British court.
The only real use for an extradition treaty should be for a foreign national to be extradited back to another country where they are wanted for an offence committed IN THAT FOREIGN COUNTRY which would also have been an offence if it had been committed in this country. Anything else is immoral and unjust. If the law was written that way then the guilty would be tried and the unjustly accused would be safe.