If it could be showed that most of the harm had occurred in Saudi Arabia and the conduct was also criminal in the UK, then it would be very similar to this case (such an extradition would be blocked for other reasons, but the question of forum is essentially the same).

It's likely that he would be found innocent if tried in the UK, which is why people are quite angry about it. No successful prosecutions have ever been brought in the UK in similar cases and the CPS wasn't going to prosecute him here.