Adrian Mitchell, FRSL, was an English poet, novelist and playwright. A former journalist, he became a noted figure on the British anti-authoritarian Left. For almost half a century he was the foremost poet of the country's anti-Bomb movement. The critic Kenneth Tynan called him the British Mayakovsky.
Found out about this collection in the Socialist Worker tribute. This seems to overlap entirely with the later American collection Heart on the Left, albeit with different Steadman illustrations. (Heart also adds some songs from Mitchell's plays and operas, all of which are probably more fun to hear than to read.)
n.b. The title refers to a child's grave which he encountered in the 1974 anti-apartheid documentary Last Grave at Dimbaza.