‘It’s no use at all,’ says Posy Simmonds in mock despair, holding up her hands. ‘I can’t tell my left from my right.’ She is ambidextrous. ‘This hand [her right] writes and draws; and this hand [her left] cuts out, sharpens pencils, throws balls, plays tennis… I can’t drive. I’ve never taken a test. I’m always on the wrong side of the road.’

Looking at these wonderful hands, elegant and almost limp, one would never suppose they had created, over the past 50 years, such a large volume of intensely enjoyable and astute drawings. Reliably funny and wise, her work ranges from Fred (1988), about the secret rock-star life of a pet cat, to Cassandra Darke (2018), a graphic novel with an art dealer anti-heroine who is part Scrooge, part Clarissa Dickson-Wright.

Simmonds is being celebrated with a UK retrospective, at the House of Illustration in King’s Cross. ‘It feels very weird…’ she tells me. ‘This stuff is mostly never on walls. It’s usually there with toast and marmalade in the morning and then wrapped around fish and chips and then in the cat tray…’.

Don’t let her modesty fool you. She is hailed as a blazing genius, adored by the literary firmament. Her graphic novels are published as literature, by Jonathan Cape. She has the same editor as Ian McEwan and Martin Amis: Dan Franklin. She has an MBE but when (in a bid to put fire in her belly) I put it to her that Osbert Lancaster had a knighthood by the time he was her age, she looks faintly embarrassed and changes the subject. Far from promoting the excellent new Thames and Hudson book about her life and work by Paul Gavett, she doesn’t know its publication date. ‘I’m just the subject.’

Starting with Gemma Bovery, her witty update of Flaubert in 1999, her graphic novels came out just as the genre itself was becoming increasingly respected — culminating in the first Man Booker prize longlist nomination for a graphic novel last year (Sabrina, by Nick Drnaso). Simmonds acknowledges how far the genre has come. Women, she says, were ‘accused of muscling in on a scene that was male, particularly the superhero scene in the US, but now there’s a whole generation of women who are completely uninhibited and drawing just as themselves…. Still,’ she grins, ‘people think you’re probably drawing bears in pinnies. You’re often asked, “And do you ever do any proper writing?”’

In person, everything about her is understated, from her blue chiffon scarf to her cautious, horizontal approach to my questioning. She was born in 1945 and brought up in Cookham Dean, where her father was a farmer. Stanley Spencer painted her grandmother’s wisteria, and she remembers peeping at him over a gravestone in a churchyard aged about eight as she and her friend watched him painting the angel kneeling on a plinth by the gate. ‘He pushed around a pram full of paints and had with him his spaniel… He gave us some sweets to go away. It was a sunny day; not a creepy encounter at all. I was absolutely aware he was a great artist.’

Addicted to comics, she illustrated her own invented pulp fiction with titles such as Bullet Vengeance and Vulture’s Hole, or parodied the racy style of a woman’s magazine in Herself which had cover-lines such as ‘Lady Whoresome reveals…’ Some issues were confiscated by matron; one makes it into this retrospective. Her best present as a child was 500 pages of Imperial ‘Elephant’ paper (about a square metre) which she filled in its entirety. ‘I liked being outside, or I liked being inside and drawing. Wet days!’ Her eyes flash with pleasure.

A tweedy country girl left to study in Paris at the Sorbonne; a sophisticate clad in black returned having ditched her course because her social life was more interesting. At Central St Martins she met her future husband, the graphic designer Richard Hollis, 11 years older than her and already father to two boys, whom she stepmothered. As a young cartoonist she contributed six saucy gags per week to the Daily Mirror; she illustrated a spot in the Reader’s Digest (‘They paid very well.’) and, drawing for the then Manchester Guardian, she raced to get her work into ‘the parcel’ before it was sent up to Manchester by train.

She shared a flat in a Queen Anne house near Doughty Street (‘Sloping floors so a pencil raced away immediately… only one lav in the garden for the whole house. We called it the “ig-loo”… All the doors and cornicing were original… Halcyon days, until we received a letter saying it was a “dangerous structure” and had to move out’). Drawing for The Spectator, whose offices were then round the corner, she hit a historical vein with parodies of Gainsborough and so on, drawing on her great love of the British satirical tradition. ‘I’m particularly fond of Rowlandson, who can be very scabrous and rude. I’ve got a print of his “Vauxhall Gardens” on my wall. It has everyone who’s anyone in it, like a 19th-century A-list.’

We skip in one breath from the black spots worn by ladies to cover their smallpox scars to how to draw Botox: ‘Botox means a rather egg-like quality to the forehead,’ she says, ‘and then there has usually been other work too, so these great lips and a sort of gutter down the middle…’ While drawing she makes faces into a large gilt mirror (a gift for the purpose from her husband) to help her nail an expression. The fine observational skills — and underlying moral indignation — of Hogarth, Gillray and Cruikshank live on in her work, whether it is puncturing the self-regard of square-jawed famous authors or posing awkward questions.

‘Why are there no beggars in affluent places like Knightsbridge?’ she asks me. Researching Cassandra Darke, she walked every day from Islington to Knightsbridge, where Cassandra lives. ‘I was so struck by how many of the houses there are empty, just hollowed-out investment boxes. I asked a doorman how many of his 60 flats were occupied and he said six.’ She loves to walk. ‘Miles and miles. For a graphic novel it’s just like a film. You have to cast the characters and choose the locations. I am a camera.’

Her first graphic novels were serialised before publication, until ‘it all got a bit hairy’ and she fell behind schedule, at one point only two weeks ahead of herself. ‘I’m so used to working fast, I thought I’ll just do 25 episodes and then jump on the back of it, like Dickens… Ha! Deadlines do concentrate the mind, but missing holidays and weekends is not… ideal.’ Cassandra Darke was published as a standalone book.

For her next project, she is ‘drawing a lot of rubbish. I’m very interested in rubbish. How rubbish attracts rubbish. Someone puts down a plastic bag of it, and then someone puts a bottle and their old lunch, and then you’ll get a mattress… Railings invite people to post litter through them…’ As we talk about railings, her observational skills humble me: she describes some particular to a certain London square — dog railings, at a low level. I never noticed these, even though I lived in said square for five years.

Another project is about servicemen and women who died in Iraq. ‘I keep lots and lots of drawing books that don’t necessarily surface.’ But this might. ‘It might. I was just very struck by the sadness, when you saw a bereaved parent being interviewed on the news and you’d see a picture of their son or daughter as a child, behind them. The waste. The terrible waste.’

She marched against the Iraq war in 2003. ‘It was very cold.’ She didn’t draw a poster, ‘but I was behind a poster of a kitten with huge blue eyes. It said “Stop the war or the kitten gets it”.’ Would she ever serve as official election artist? She shudders at the word ‘official’.

Two recent retrospectifs in Paris and Brussels saw her interviewed by journalists agog about Brexit. ‘I was asked again and again about “le backstop”, and “le point sensible” [red line]. I can’t even talk about this stuff in English, let alone in French.’ She has drawn Brexit faces from the TV during news bulletins.

Saying goodbye, I hesitate to shake her hand, because, well, it is so precious. It could be the drawing one. I forget which is which.