Why has the UK done a deal with Iran for Nazanin Zaghari-Ratcliffe?

The release of Nazanin and Anoosheh comes against a background of a bigger diplomatic game being driven by world events.

As Russia’s war forces the west to look elsewhere for its oil and gas, there’s renewed focus on restoring relations with Iran. And today Boris Johnson was visiting Saudi Arabia, in the hopes of securing alternative supplies of energy, despite serious concerns over human rights.