“One of the great laws of war is ‘Never invade Russia’,” as the probably apocryphal Field Marshal Montgomery line goes. It stands as pretty solid advice. Still, that didn’t deter Arctic Monkeys, Hurts, Foals, Jessie Ware and Savages from launching a British invasion of their own this summer, braving 30°C temperatures for the inaugural Subbotnik festival in Gorky Park, in the centre of Moscow.