[chiph]

The host country has the right to accept or deny a diplomat's credentials. Here's the US Ambassador presenting his credentials to Queen Elizabeth.

https://www.youtube.com/watch?v=S4E9LMK46oo

[bainsfather]

According to former ambassador Craig Murray, this applies only to head of mission (ambassador) : https://www.craigmurray.org.uk/archives/2018/01/ecuador-and-...

A host state may expel a diplomat, but may not remove/ignore their diplomatic immunity.

[chiph]

So.. problem solved? Make Julian a diplomat, let the UK Persona-Non-Grata him, requiring him to "return" to Ecuador?

Of course, there'd also be the problem of other countries denying the plane access to their airspace. They're probably upset with him over his role in the Snowden event. https://en.wikipedia.org/wiki/Evo_Morales_grounding_incident