QUENTIN Blake has not left the building.

Blake's summer exhibition at Nunnington Hall has made way for a retrospective selection of the watercolours, original book illustrations and lithographs of his late friend, Paul Hogarth, and among the portraits is Hogarth's 1993 study of Blake, executed in pencil and dashing stripes of watercolour.

Blake looks avuncular, soft eyed yet twinkling with amusement: just as he came across in our interview last month.

"Paul was a bit nervous about painting people," reveals his widow, Diana Hogarth. "He worried that they wouldn't be satisfied or that he hadn't shown them in a good light, or that the portrait was unflattering."

Did he ever paint Diana? "No, he didn't. I never asked him to, but then he never asked if he could paint me," she says.

His portraits of Blake, Graham Greene and Robert Graves suggest it was a missed opportunity.

Portraiture was only a small part of his portfolio. The art of book illustration - hence his friendship with fellow illustrator Blake - was his calling card, whether complementing the writing of others or in his own travel and walking books.

Over the years, Hogarth collaborated with writers Greene, Graves, Doris Lessing, Brendan Behan, William Golding, John Betjeman and Lawrence Durrell.

Remember when seemingly every guest bedroom had to have a copy of Peter Mayle's A Year In Provence? The illustrations were by Hogarth.

Remember the joys of English literature at school? New Penguin's gothic series of Shakespeare book jackets, most memorably the haunting Hamlet vignette of a raven perched on Yorick's skull, are perhaps Hogarth's most familiar works of all.

"Paul loved literature. He was always reading and his library was immense," says Diana.

"When we were travelling there was no time for reading, but when he was in the studio, waiting for the watercolours to dry, he'd read and play music - he loved music as well. There was a lot of time spent waiting, so a great deal of his reading was done in that time."

Hogarth was meticulous in his preparations for his illustrations. "He always read the full manuscript or draft before doing his artwork. He considered the reading to be part of his work, and different from reading for pleasure," Diana says.

Did he like to meet the writers to discuss his artwork? "That wasn't so important to him. He did Graham Greene's jacket covers for almost 30 years but they didn't meet for some considerable time. He wanted to get into the characterisation; that's what mattered to him, rather than finding out more about Graham Greene or meeting him."

Hogarth pursued a career in illustration against the wishes of his parents.

"They didn't want him to be an artist; his father was a Cumbrian butcher, and they wanted him to go into banking. At that point Paul decided he had to do something; he won a scholarship to the Manchester School of Art, and off he went. "It was that teenage thing of doing your own thing as a student," Diana recalls.

He was soon to do his own thing again. "He became a member of the Communist Party in the 1930s and went off to fight in the Spanish Civil War with the International Brigade, but when it was discovered that he and the others with him were too young, they were sent back, but by then he had lost his place at the school of art."

Nevertheless, art was in his blood, and after doing poster and camouflage work in the Second World War he became involved in the radical magazines of the early post-war years, illustrating the likes of Circus and Our Time. He also travelled Communist Europe, working alongside Ronald Searle in Yugoslavia.

"He noted that Ronald was a compulsive worker, doing two or three drawings a day, and he learnt a great deal from him. Right up to the time he died in 2001, if he was working Paul would do two pictures a day, sometimes more."

Hogarth progressed from pencil to ink to embracing watercolours in the mid-1960s, although he would always start with a pencil. "He would use rulers to get things straight at the start, and though wouldn't rub out the lines, he would then forget about them," says Diana.

"It's strange: some people think the buildings in his pictures look as if they're about to fall down - although they're not - because his watercolouring isn't always as straight as the pencil lines."

The best examples of this Hogarthian characteristic are his mid-Nineties watercolours of National Trust properties, a commissioned series that includes Fountains Abbey lit up by fireworks. The Nunnington exhibition is only the second occasion the series of ten has been shown together: one of many reasons to savour this journey through Paul Hogarth's artistic life.