Six months ago Mr Marriott, 35, of west London, started to train as a teacher on a school-centred scheme in Wandsworth.
It was no whim: for the previous three years he had been a volunteer in primary schools working with children individually or in small groups on reading and writing, while continuing his career as an author and freelance journalist.
He said: "As a volunteer there was no pressure of class management, you got to know the children and their sense of humour. I really enjoyed it." He decided to combine writing - which he still continues to do - with teaching part-time.
But after a month, he left. He said: "The course was fantastic, but I had a dawning realisation about what it entailed. I was interested in the theory of education, but I wasn't up to rolling my sleeves up at the chalkface. As a teacher it is full-on from start to finish.
"It is one of the most demanding jobs you can do. My admiration for teachers was incredibly high before, but it is higher than ever now.
"The workload is unrealistic. If I had a two-and-a-half-day job, I could see it spilling into four days."
Research from Liverpool University shows 12 per cent of trainees drop out of courses, and 30 per cent who complete courses do not go on to teach.