Imagine the house of a man who in the 1940s was the wealthiest self-made man in the UK.  An industrialist who during his lifetime gave around £1 billion to charity in today’s terms.

Walls covered in Rembrandts and Monets? Vistas of formal gardens and lakes? At the very least a gold tap or two?

Nuffield Place, designed by a pupil of Lutyens, built in 1914 and acquired by William Morris, later Lord Nuffield, in 1933.

Probably the last thing you’d conjure up would be “school-of-Hyde-Park-railings” art and carpets covered with stains from his wife’s wayward Scottie dogs. But prepare to be surprised when you enter Nuffield Place, home of the late Lord Nuffield, near Henley in Oxfordshire.

When I walked into the garden of this recently opened National Trust house it was  like arriving at a vicarage fete. Bunting was strung across the 1930s-style Coronation Cafe and families clustered on the lawn tucking into sponge cake with cups of tea.

Visitors to Nuffield Place had parked their vintage cars outside the house.

Some fabulous vintage cars were parked outside, their owners milling around in flat caps and tweed. The scene was set for stepping inside the world of William Morris (1877-1963), a man who left school at 15, began a bicycle repair business with £4 capital, then moved into cars in a massive way.

By the mid 1920s Morris Motors Cars was earning its founder a fortune. But instead of spending it on a fancy home he gave away the money to medicine and education. His Nuffield Foundation, College and hospitals are still active today.

As I explored the house I was struck by visitors’ exclamations: “That’s just like my grandmother’s dressing table” and “I had one of those when I was a child.” It’s a perfect time-capsule of mid-20th-century life and of someone whose driving force was business and benevolence, not showing off to guests.  It’s a place to delight in the quirky innovations and gadgets that Lord Nuffield loved, such as his automatic match striker in the drawing room.

Visitors are free to ramble through the pine-panelled billiard room and the sitting room with its wireless and 1950s-style cabinet TV.  Upstairs is a dressing room with the one display that shows this is no ordinary middle-class home: its owners’ velvet and ermine coronation robes. There’s a sunroom full of equipment that Lord Nuffield liked to tinker with, including fire extinguishers and an ultraviolet lamp.

But for me the house’s highlight was Lord Nuffield’s bedroom and more specifically the huge tool cupboard by the end of his bed.  Every man has to have his shed and how luxurious to have it at your feet: shelves packed with clocks, wires, screwdrivers and even equipment for mending his own shoes, with stick-on soles.  In among them nestle curios such as his appendix in a jar.

The multimillionaire’s bedroom, with furry hot water bottle, curiously wired reading lamp and bedside sword.

Inside the bedroom tool cupboard, just as he left it: Lord Nuffield’s pickled appendix and equipment to mend his own shoes.

So who was this dynamic entrepreneur who preferred to hunker down in padded sofas rather than to schmooze and entertain? Let’s leave the last word to a plaque presented to William Morris by his golfing buddies, dedicated to “A sportsman and good egg”.

* Even if you don’t have a vintage Morris car you can motor to Nuffield Place from London for a great afternoon out.

National Trust photographs, from top, courtesy of James Dobson, (vintage car by London Slant), John Hammond and Cristian Barnett.