Sir Keir Starmer was midway across the Atlantic en route to the G20 summit in Rio de Janeiro when some unexpected news broke.
Reports in the US revealed that Joe Biden, the outgoing president, had authorised the use of long-range Atacms missiles against targets in Russia.
The prime minister and his most senior aides, gathered at the front of the aircraft, were already aware of Biden’s decision, which had been taken three days earlier — but they were not prepared for the news to leak so soon.
With journalists travelling alongside the prime minister to the summit, Downing Street knew that it would have to say something about whether British-manufactured Storm Shadow missiles could also be used against targets in Russia.
A decision was taken