Commissioner of the Metropolitan Police Sir Mark Rowley is taking a page out of the Lloyd Evans playbook
Not really. There is an extradition treaty between the US and UK and a well-established history of exchanging suspects for trial.
True, some cases are more controversial, and the US does have quite a poor record of complying with international agreements and laws when it comes to allowing their own citizens to face justice abroad for their crimes (in stark contrast to their habit of invading other countries or putting serious pressure on other governments to extradite people they want to see in US-run courts), but still, the situation is hardly comparable to the relationship between the Croatian judicial system and the UK or USA.