As Nicola Sturgeon calls for further action against the Putin regime, perhaps she should reflect on how her demand for independence undermines the security not only of the UK but of Nato. Apart from the disruption and economic uncertainty that another referendum would bring, if Scotland were to separate from the world’s fifth-largest economy it would be left defenceless, and the most important submarine base in Europe would be closed. Faslane is a vital cog in the machinery of Western defence, and without it, we would be open to Putin’s nuclear blackmail. An independent Scotland would be a gift to Putin. The SNP should end its opposition to nuclear weapons immediately and drop its foolish separation agenda because unity is strength. William Lonskie, Lauder, Berwickshire.