Trenton Oldfield is part of our eccentric heritage. We should cherish him, not imprison him

The greatest book of the modern age, in case you were wondering, is Rogues, Villains and Eccentrics: An A-Z of Roguish Britons Through the Ages by William Donaldson, which celebrates its 10th anniversary in print this year.

After an extensive survey of this important work I've concluded that, historically, British rogues come in two main types. The first is the aristocratic English eccentric, like the 8th Earl of Bridgewater who shod his many dogs in handmade boots, and regularly invited them to his table as dinner guests, or the reclusive 5th Duke of Portland who communicated through a letterbox in his bedroom door and ordered the construction of a 174ft- long subterranean ballroom under his grounds. Like a pedigree show dog prancing on hind legs, this type is a marvel to behold, but does not bode well for the continuance of the line.

That's probably why it's the latter type – the eccentric as protester – which is more in evidence today. Yesterday Trenton Oldfield was found guilty of causing a public nuisance and now faces a possible custodial sentence. He protested Government cuts by swimming into the path of the crews during this year's Boat Race. Oldfield is Australian by birth, but a true British eccentric in every way that matters. Firstly, because he correctly values two of our nation's greatest achievements, the NHS and the welfare state; and secondly because he's got a very funny way of showing it.

Like Stephen Gough, the "Naked Rambler", or the intruders in tuxedos who presented a former HMRC boss with a "corporate tax avoidance" award at a City dinner, protesters are usually given humourless short shrift, regardless of the silliness of their protest or the seriousness of their cause. The dinner guest who ejected the protestors, for example, called them "trespassing scum" and told them to leave "before we set the dogs on you".

But British heritage doesn't just belong to senior tax lawyers and Crown Court judges. It's ours too, ours to define and ours to defend. We may, like Oldfield, define it as the NHS and we may defend it by dancing the bogle in our underpants, showering in baked beans or however else seems expedient at the time.

I like to think Oldfield, Gough and the intruders would have made it into a revised edition of Rogues, Villains and Eccentrics. Sadly, William Donaldson died in 2005, but being a great English eccentric himself, he did so only after taking up crack cocaine in his fifties, spending his last £2,000 on a glass-bottomed boat in Ibiza and moving into a brothel on the Fulham Road. Having made such an important contribution to our culture, he was entitled to do exactly as he pleased.