Someone appears inadvertently to have left a toilet in the forest.

It is perched on the edge of our iron age fort with a view to die for. It sits stolidly at the summit of a plummeting earthwork planted with tall beeches and hazels. It has the air of a union man.

It does not blend in: it is bright blue. It is the epitome of utilitarian practicality, though. I wonder if the workmen who have been there for a month have remembered yet that they left their toilet behind?

I can see them all, in the middle of a cup of char, just about to crank up the digger, when someone claps their hands to their forehead.

“Stone me, left the toilet behind.”

Better not have too much tea, then. And steer clear of the bran muffins.

Still, this incongruous addition to the forest has its uses. While I haven’t tried the door (yet), I can imagine it could be very useful for dog walkers and runners, caught short after stumbling out into the early morning, desperate to get in some exercise before the busy day begins.

But there is nothing pretty about it. We leave pretty and impractical to the follies.

These are buildings conceived and built in whimsy. Some authorities, including the Oxford Dictionary, have branded them the costly result of foolishness.

This morning I heard some news about a folly which is rather special to me.

My old college is housed in one of the most extravagant Georgian buildings of its time: Strawberry Hill, the frothy confection created by Horace Walpole.

Walpole was a poet, writer and MP from the top drawer of society. He was the fourth son of prime minister Sir Robert Walpole. He had spent the Summer holiday of his eighth year by the river in Twickenham, and he loved it.

At 30 years old, he realised his dream of acquiring a small house near the Thames at Strawberry Hill. And then began a life’s work to transform a small, unassuming country house into a gothic castle.

He was at the forefront of this ‘gothick’ craze of the 18th century. While reasoned liberals favoured the measured style of classicism, conservative minds looked back to mediaeval times to inspire a romanticism, and an expression of all that was great about Blighty.

Ever industrious, Walpole was not content with asking friends to advise him on this ripping new adventure.

No, he appointed a committee. It was called a ‘Committee of Taste’. It consisted of himself, John Chute – Walpole’s ‘Oracle Of Taste’, whom he met while travelling – and Richard Bentley, a skilled artist and draftsman.

This was not a scholarly trip down memory lane. It was an eclectic bag of tricks that inspired Walpole’s glorious folly.

He visited gothic buildings whenever he could. Whenever he couldn’t, he pored over books of mediaeval architecture. He sketched the details he liked, whether domestic or ecclesiastical, and then he found a way to incorporate them into his castle.

Walpole was very up-front about this. He told a friend in a letter that the rooms at Strawberry Hill were ‘more the works of fancy than of imitation.”

Thus, a gothic south front was added to the building, complete with battlements and pinnacles, clad immaculately in white plaster; a round tower was built: and inside was a feast of gothic staircases, fireplaces, stone arches, wallpaper and fretwork.

He spent £21,000 on this whimsical wonder, a fortune in the eighteenth century. The architecture of St Pancras Station and the Houses of Parliament followed where Strawberry Hill led the way. And today we have learnt that Walpole’s folly reopens very soon after a thorough restoration, which has cost of £9 million.

Walpole described the house as being made of paper and fabric. It wasn’t concieved as being a permanent gift to posterity. And yet here it is, hundreds of years later, being celebrated not in spite of, but because of its folly.

So why did he do it? Why does anyone make something pretty and foolish and expensive? A clue comes at the end of Walpole’s Parish Register of Twickenham, a list of the local VIPs. He writes: “Enough if I consign, to lasting type their notes divine: Enough, if Strawberry’s humble-hill the title page of fame shall fill.’

And there it is. The F word: fame. All is vanity, and we will go to many lengths to gain fame and occasionally  notoriety. A place in the history books can be secured  through gainful toil, great leadership or high birth. But a place may also be gained through other means at one’s disposal.

As Becky Sharp ably demonstrated.

She was the work of a fellow hack, William Makepiece Thackeray. This man knew what it was to skim by the seat of one’s nineteenth century britches, eking out a living by writing.

On an erudite day he might contribute to the Times: on a less august, and slightly more wicked day, it could be Punch. He said himself, he ‘wrote for his life’.

The man was incisive, and clever and occasionally merciless. In his great work, Vanity Fair, he seemed to be able to see through the surface glamour and vanity of society to the human dealings beneath.

Becky is the ultimate anti-heroine. She is clever and resourceful, with utter focus and total ruthlessness. She cares, it seems, for no-one. Her child is neglected and she treads on others to reach ever greater heights as she climbs the English social ladder.

Around her, but somehow a little less vivid, are the good guys,  gentlewoman Amelia and military man Dobbin, who have built their life on solid values. They go through intense suffering as they tramp through a veritable soap opera set in the Napoleonic Wars. And Becky gets very close to the top, by championing vanity.

Vile woman, but oh, so colourful.

She uses every means in her power to court fame, using vanity. There is nothing utilitarian about her methods. In the end, the tower of notoriety she built amongst the upper classes was a tall, striking folly.

Like sugar, a little vanity goes a long way. It’s fine for building follies, but not a great foundation for a life.

Give me the honest, utilitarian comfort of a toilet in the forest any day.