For three years in the late 90s, Sergey Lavrov was my Russian counterpart when we represented our countries on the UN security council in New York. Despite some obvious policy differences, Lavrov never played the UK false; he was a serious and creative negotiator, with a good sense of humour and a passion for the English language and its literature. To decline Lavrov’s invitation for our new foreign secretary to visit Moscow (Report, 10 April), just when new tensions show such contacts are most needed, seems ill-advised. Hard too to square with the windy rhetoric, since the Brexit referendum, that Britain will re-emerge as a world power rejuvenated.

John Weston

Richmond, Surrey

• Paul Mason’s article (G2, 11 April) is characteristically thoughtful and intelligent but his premise is presumptuous. “I am convinced on the current evidence that Assad’s planes dropped chemical weapons on the rebel-held town of Khan Sheikhun on 4 April,” he writes, accepting immediately thereafter that “verifiable forensic evidence” is still awaited.

So of what does his evidence consist? Such circumstantial attestation as has been mentioned is either capable of being contrived (in Syria or Washington) or subject to the omertà of supposed security considerations. That leaves motivation, and here there is a gaping hole. Assad’s forces were moving towards an endgame. What possible reason could they have for endangering the hard-won balance of advantage by committing a gratuitous act that they would know could only rouse worldwide antagonism and possible retaliation? Believing Assad to be a bad man is hardly the basis for a policy, but believing him also to be stupid errs on the reckless. Until some convincing explanation for the strategic and/or psycho-political advantage that Assad sought is offered, the jury must remain out.

W Stephen Gilbert

Corsham, Wiltshire

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