Indeed, Great Britain did sign an agreement with Persia.
The agreement explicitly stipulates: When Persia is at war with any European country, Britain will provide financial support or directly send troops from India to aid Persia.
Funds have indeed been provided by the Foreign Office, but the exact amount is uncertain.
As for sending troops directly from India to support Persia, didn't you notice the 'or' in front?
The British Government certainly cherishes its longstanding relationship with Persia, but due to traditional friendship and economic ties with Russia, as well as having a common enemy in France, Britain must cautiously deliberate when confronting Russia in alliance with Iran.
Those Persians who failed to understand this lost their territories, and a certain former high-ranking officer from Scotland Yard was taught a lesson in Liverpool.
Of course, on the other hand, there's no problem with Russians carving off some land from Persia and asking for some reparations.
