The humour - her pictures are overflowing with it - is never over the head of her small reader, but equally entertaining to the adult, who can join in the pleasure even after countless re-readings.
Illustration was Janet's second choice of career. She trained as a teacher at Sunderland Training College, where she met her husband, Allan. She changed course to study design at Leicester Polytechnic, and a great creative writerillustrator partnership began. It was not easy at the start (it rarely is). Some of their first picture-book ideas were rejected. It was Burglar Bill (1977), followed by award-winning Each Peach Pear Plum (1978), which put them firmly on the road to international fame.
Janet's soft earth-colour washes are restrained; the spice of her characterisation is in her sprightly line. There are no gimmicks. Her skill is in effortlessly bouncing off the text, keeping the whole dance flowing from page to page, ending with a satisfying finale.
In Starting School, the copy-book type-face is interspersed by a cast of little figures who touchingly describe the activities of a first term. The humour is reassuring and the detail repays attention. In the same way, The Baby's Catalogue humanises the all too recognisable items of babyhood.
Precisely observed interiors are one of the strengths of Janet Ahlberg's work. We long to know, for instance, as Burglar Bill sits down in a warm ochreish glow to his well-earned tea of fish and chips and KO sauce, what really prompted him to appropriate that box of six dozen hairnets.
The interiors of Peepo!, set in the 1940s of Allan's childhood, give the flavour of homely make-do which characterises that period. This era is affectionately revisited in the line drawings which are dropped in, EH Shepard-like, to the text of The Bear Nobody Wanted. In the Happy Families series, the Biff family at home, busily engaged in activities such as chess and playing the piano but all wearing boxing gloves is a tour-de-force.
In The Jolly Postman - one of Allan's most inventive ideas - and The Jolly Christmas Postman, Janet matched him all the way, setting an atmosphere which is just right, not quite never-never land, but certainly not the real world. The Jolly Pocket Postman, her last book, will be published next year.
Janet was not physically strong and her working hours were very rigorous. Her drawings have an airy innocence which makes them appear to have dropped simply on to the page, but, as with all highly accomplished styles, they were the product of acute observation and sustained concentration. Even towards the end of her life, every drawing Janet did displayed a joyous vitality and lightness of touch.
I once heard Allan liken making picture books to blowing soap bubbles. But these particular bubbles, so softly coloured and elegantly simple, are made of enduring stuff. They will live on to give pleasure to countless children and grown-ups for many years to come.