Children: Books for...

Alan Garner writes in The Times on his childhood reading - which was, of course, everything he could get his hands on. He ends with a puzzle, asking if anyone can identify a series of books which impressed him deeply, but whose title and author he cannot recall:

The novels were built around a boy's discovery that the doors of pillar boxes would unlock at unpredictable times to disclose a stair going down to another land. In it was a garden, and in the garden a girl. The other constant was a wise but erratic old gentleman, who led the children into magical dangers. The girl gave the boy a handkerchief made from her dress, and told him that as long as he kept the handkerchief they would meet again. Each book ended with the poignant separation on the stair. I have not seen the books since 1943, and I still have the handkerchief.