The horses were the easy bit to paint, Sir Alfred Munnings said. It is the aristocratic women on top you have to watch out for.

A set of unpublished letters the renowned artist wrote to his second wife have revealed his frustrations at the whims of the society figures who commissioned him to paint themselves and their horses.

There was the Duchess of Westminster who wanted her breasts and feet reduced in size.

“These riding women imagine they look entirely different to what they are,” Munnings wrote of his experiences to Violet McBride in the early 1920s.

Then there was Lady Torrington, who sent her horse to Essex for him to paint, forcing his hasty departure from Hampshire.

The English painter Sir Alfred Munnings, surrounded by a few signature works.

And there was the Master of the Belvoir Hunt, Major Tommy Bouch, “who is spoiled with all his riches … He has no love for a horse whatever.”

The letters, which are being published by the Munnings Art Museum, Dedham, Essex, this month in a new book, Yours with love AJ, highlight the misery felt by the artist, who is now recognised as one of the world’s finest equine painters.

The letters were written between 1920 and 1922 as Munnings travelled across Britain and France at the beck and call of various aristocratic families.

While he had some acclaim after being commissioned as a war artist and was already admired for his equine paintings, it would not be until 1926 that Munnings was elected a full member of the Royal Academy, the institution of which he became president of in 1944.

“These riding women imagine they look entirely different to what they are,” Munnings wrote.

His letters recount what he describes as his “miserable existence” in the early 1920s — shortly after marrying McBride following the death of his first wife, Florence Carter-Wood — and how he is “very sick of this job”.

During his journeys across Britain and France Munnings encountered many of the most renowned figures of the age, including Field Marshal Earl Haig and Baron Rothschild, whom he described as “absolutely the kindest fellow I’ve ever met”.

Munnings’s Portrait of Mrs. Bayard Tuckerman.

In 1921 he travelled to Eaton Hall, Cheshire, having been commissioned to paint the portrait of Violet Nelson, the second wife of Hugh Grosvenor, the 2nd Duke of Westminster.

One letter to McBride said that at first the duchess was delighted with the portrait: “I think it’s marvellous Mr Munnings!!” — (all because she looks tall, slim and graceful as no woman ever did look on a horse!).

Munnings continued: “There’s just one thing more only one!!” — “I want you Mr Munnings to take a little of my chest — a wee bit!! … Oh Mr M — there’s still one thing more — Do you think my foot is too large. Can you take a little piece more off it?”

He wrote that the duchess later “said her eyes were too small then too large then the mouth then the bowler hat — & my God when I began the habit — it was never right”.

“Anyway she’s all but spoilt her picture and reduced me to a miserable state of nerves … Another job of this sort would send me mad,” he wrote.

He also wrote of his disbelief at the success of his fellow portraitist Philip Alexius de Laszlo, whose portraits were “awful things … sloppy … he gets huge sums for these … my blessed horseback portraits are no go for money making”.