Boris Johnson under pressure to explain whether position has changed after tweet blaming Moscow is deleted. Boris Johnson is facing embarrassing questions over his claims that Russia had produced the Salisbury nerve agent after it emerged that the Foreign Office had deleted a tweet blaming Moscow for the attack. With the foreign secretary already under pressure over his remarks two weeks ago that a Porton Down scientist had been “absolutely categorical” that the novichok had originated in the country, Jeremy Corbyn accused Johnson of “completely exceeding the information he had been given” after the emergence of the deleted tweet. But...