MOSCOW – The gulf between Russia and Britain widened Friday as they cranked up pressure over a nerve agent attack and a suspected murder in Britain that have deepened Western worries about alleged Russian meddling abroad. Britain’s foreign secretary accused Russian President Vladimir Putin of personally ordering the poisoning of ex-Russian spy Sergei Skripal and his daughter, Yulia, describing it as the most brazen such move since World War II. Putin’s spokesman denounced the claim as “shocking and inexcusable.” As relations between the two nations sank to a new post-Cold War low, nearly two dozen Russian diplomats in London were packing their bags to leave Tuesday after an expulsion order from Britain.