He lives his own version of the good life in two gamekeeper's cottages knocked into one, with gas but no electricity. (His 400-page tome was consequently written in longhand 'and took several years'.) He shares his life with Claire Clifton - a loquacious American food writer who has written books with such delicious titles as Edible Gifts and Edible Flowers. The new book declares them both to be 'happy recluses in a two-acre garden, cultivating flowers, herbs and oriental vegetables'. Not so happy, it would seem. Colin wants electricity - he cannot face the annals of homosexuality without a word processor.
One enters the portals curious to gauge what life is really like in a house that has been held up to the salivating brick-bound readers of Country Living magazine as an emblem of rustic free- range living.
It's amazing how a glossy photograph smooths rough edges. We sat down in some saggy-baggy chairs and he explained how vegetarianism had evolved over the centuries. 'The distance between man and domestic animals has allowed him to sentimentalise them, to see them as rustic accessories to the landscape,' he says. 'In this respect the industrial revolution did a great service to animals. How an animal lives before it dies is often uppermost in people's minds when they give up meat.' The hard core of vegetarian beliefs are 'mystical and philosophical - a holistic belief that we are all concerned with everything alive and living.'
The Heretic's Feast, as his history is called, would seem to bear this out. In it Spencer has really compiled a history of unorthodox thought in relation to food from Egyptian times to the present. It is rather like reading a history of the world in 12 1/2 chapters. He found that most heretical societies, who were searching for a divine or moral truth, endorsed (and usually embraced) vegetarianism. Though, it has to be said, he has some very unkind things to say about beans. (The curious can find them on pages 44-46.)
'Vegetarians have always been outsiders, in a sense, always challenged the received norms.' He is very fond of the Manicheans, whom he passionately defends from 'the grubby, highly slanderous picture left to us by Christian saints and writers'. The Manicheans based their philosophy on light and therefore ate plants, which contained light, rather than flesh, which was rotting. Spencer comes as a fellow traveller to the world of the heretic. He finds the general orthodoxy of present society boring. 'Well, not boring. Hypocritical. All these beliefs holding society together like cement. No one really thinks; they just accept.' Not so the Manicheans, the Gnostics, the Fabians, the 'Counter Culture' of the Sixties. And not so Colin Spencer.
Before he met Claire Clifton, he lived for 14 years with a theatre producer. 'I should only have stayed for four really. It was a nice life,' he reflects, recalling houses in London, the Mediterranean and his present cottage. 'But in the end I felt he was sapping my creativity so I left with a suitcase and a typewriter.' He continued his career as a novelist and playwright, completing nine novels and a play, Spitting Image, about two men conceiving a child.
Before that he had a bitter divorce case, being pursued through the courts for 'homosexuality and drunkenness' by his wife, who tried to stop him seeing his son. ('You can imagine the sort of view the judge took of all that.')
He feels that people don't know what options they have in life. 'Most people just sit back and think fate will decide. All this is rubbish to my mind.'
Spencer has always experimented but rarely committed himself. He has been with Claire Clifton for seven years. As she doesn't drive they live a closely entwined life, he chauffering her around to local market towns.
Who better to write about outsiders than Colin? As an established expert in food writing (he is vice-president of the Guild of Food Writers and has written 12 cookery books) and as an established nonconformist, he was in congenial company with the great and the good of vegetarian history. 'I liked the way most vegetarians disputed the norms of society and helped to move it on. All these sects, people and movements I write about have been noted by historians, but I don't think that anyone has looked at their diets or noticed that they were all vegetarian.' He says he was staggered that even the vegetarianism of Leonardo da Vinci has been ignored in all but two of the 60 biographies of him, 'yet it was crucial to his beliefs. It's this same old attitude. 'Oh, it's only food. It's not serious'.'
Indeed the very fact that meat-eating has been so central to the evolution of society is - so runs Spencer's argument - one of the factors that has made vegetarianism difficult to establish itself. Meat was used in sacrifice to please God; it was also a sign of a primitive society's wealth, success and - in biblical terms - man's dominance over 'every creeping thing that creepeth upon the earth'. If you gave up meat you were - and still are - seen to be putting yourself outside society's parameters.
'It is quite amazing how threatened people still feel when you say you don't eat meat,' remarks Spencer. 'Often people think you are taking the high moral ground and - quite understandably - resent it. People think that you cannot possibly be a gourmet and a vegetarian.'
For lunch we eat a stimulating and stylish mixture of roulade of Swiss chard, with sprouting broccoli tossed in sesame oil and ginger and new potatoes with a peanut dressing. There is a pear and cherry clafoutis to follow. It is delicious.
Meanwhile figures tumble from his lips: more than 60 per cent of the Third World's grain is imported to feed our cattle. Which is like saying that 13 million starving children could survive on what we feed to our cows in one year. He would like to see meat production fall to one quarter of what it is today, which would enable all livestock to be free-range. Today 8.2 million in the UK, the greatest number of people ever in a Western society, have renounced red meat. It's all tucked away in the book.
Spencer was inspired to write the history when he read a piece by Shelley admiring 'the Pythagorean diet'. ('In those days no one was called a vegetarian, a term only coined in 1847 by the Vegetarian Society,' explains Spencer.) Meanwhile, it was the ascetic Pythagoras - today chiefly remembered for a mathematical formula - who was held up as the expositor of the alternative lifestyle.
'Pythagoras studied in Egypt with a sect whose priests wore only cotton and whose sandals were made of papyrus. They refused to have anything to do with meat or animal by-products.' Pythagoras - like the Hindus and Buddhists who were coming into being at roughly the same time - refused meat, as he believed in the transmigration of souls.
Then, animal rights rarely existed as an issue in its own right. Normally people gave up eating meat because they associated it with death or killing, or, if they believed in reincarnation, with possibly eating a deceased relative. 'The term animal rights was first used by Brigid Brophy in the early Seventies, but there was a concern for them before that.' Spencer claimed that when doing his research he was most struck by the concern for animals shown by writers of the ancient world and the Renaissance, such as Plutarch and Sir Thomas More.
So who were the real villains of vegetarian history? 'The Church has a particularly bad reputation,' says Spencer. In medieval times there was the criminal prosecution of animals, when animals considered dangerous to man - such as dogs, cats, lice, rats or locusts - could be tried and sentenced to death. Christians were quite hypocritical, believing that no animals could be saved as they were without souls, while also believing they could be possessed by the devil. The first thing Noah did on reaching dry land was to sacrifice two of his cargo giving the green light for mankind to eat red meat.
The other veggie villain is Hitler, though admittedly he does fit into Spencer's theory in that he was certainly an outsider who wanted to change the norms of society. 'The thing about him is that he made no effort to proselytise and banned vegetarian societies and literature. He made no attempt to stop others eating meat when they dined with him, which is rather odd for a dictator, don't you think?'
The major irony of Hitler's vegetarianism is that it challenged the whole view that vegetarians lacked aggression and after the war this assertion was quietly dropped from vegetarian literature. 'A good thing too,' says Spencer. 'Being a vegetarian was probably the best thing Hitler ever did. There's too much of this high moral tone associated with vegetarianism. In the end it only makes people want to say, 'Bog off'.'
'The Heretic's Feast, A History of Vegetarianism' is published by Fourth Estate on 5 April, price pounds 20.