John Banville's 1995 essay at The New Republic:
This was a very low period for Waugh. There was an urgent necessity for him to find a way of making a living, and eventually, with deep foreboding, he took a post as a teacher at Arnold House Preparatory School on the north coast of Wales. This grotesque establishment was the model for the hilariously awful Llanabba Castle in Decline and Fall. He did not stay there for long, and found another teaching job at a more nearly normal school in Buckinghamshire, from which eventually he was sacked, apparently for drunkenness. Waugh was not cut out to be a teacher.
He did not really know what he was cut out to be. He had started to write, and some short stories had been published, but he had not yet given up hope of being a painter. He also spent a brief, happy few months taking carpentry lessons with a view to embarking on a career as a cabinetmaker. He did some journalistic work, and began his first book, a life of the Pre-Raphaelite painter Dante Gabriel Rossetti, but the most important event of these years was his meeting Evelyn Gardner on April 7, 1927. (They would come to be known to their friends as He-Evelyn and She-Evelyn.)
more here.