The report of Trudi Warner’s trial (Judge throws out case against climate activist who held sign on jurors’ rights, 22 April) being thrown out on the basis of jurors having the right to acquit a defendant based on their conscience, relates directly back to the so-called conscience clause introduced by a number of Quakers, including my grandfather, John Henry Barlow, and his MP cousin Sir John Barlow into the 1916 Military Service Act, which would have made military service compulsory. This clause enshrined in law for the first time the right to claim exemption from military service on grounds of conscience. From 1757, Quakers had been exempted on conscientious grounds, but the wording was left undefined and it had to be dealt with on a case-by-case basis. A direct result of this new clause was the founding of the Friends War Victims Relief Committee by Philip Noel-Baker, eventually becoming the Friends’ Ambulance Unit, which served bravely in two world wars. Antony Barlow Wallington, London