All prime ministers end up being their own foreign secretary. Keir Starmer started off as one. He has been moderately successful in foreign affairs, but has gained no credit for it from the British electorate.
He has played a role in rallying Europe to the defence of Ukraine. This bore fruit at what we might call the half-baked Alaska summit between Donald Trump and Vladimir Putin. The meeting failed to end the war in Ukraine, but that also means that President Trump did not sell out the Ukrainian people, which he has threatened to do.