[Skybird]

Vienna Convention on Diplomatic Relations 1961 (link)

Article 22

1.The premises of the mission shall be inviolable. The agents of the receiving State may not enter
them, except with the consent of the head of the mission.

2.The receiving State is under a special duty to take all appropriate steps to protect the premises
of the mission against any intrusion or damage and to prevent any disturbance of the peace of the
mission or impairment of its dignity.

3.The premises of the mission, their furnishings and other property thereon and the means of

transport of the mission shall be immune from search, requisition, attachment or execution.

Britain ratified this convention, like 186 other countries also did.

Either you play by the rules, or you play not by the rules. Just to sometimes do, and when it is opportune: sometimes not - that is what renders you unpredictable to the max.

It makes maintaining diplomatic relations pointless.

For Ecuador, violating the embassy in London in principle is a justification to declare a state of war. Whether they would go that far I doubt, but that is how it is.