The utilitarian pizza is available for experimentation in a way that other classic dishes aren’t

There's a rash of abominable dishes being served up in the name of pizza. But, asks Will Dean, whoever thought it needed reinventing anyway?

As a foodstuff, the pizza has more bastard offspring than Game of Thrones' King Robert Baratheon (note for non-nerds: a lot). Since Queen Margherita put her name to Naples' signature dish in the late 19th century, the pizza has spread through the world with a success that even Joolz Caesar himself couldn't match.

On that journey it's been transformed into gooey deep-pan; had every topping imaginable thrown atop its hallowed mozzarella and, among other Pizza Hut-induced indignities, had its crusts stuffed with cheese and – earlier this month – its circumference spanned with hot-dog meat.

These shifts happen because the utilitarian pizza is available for experimentation in a way that other classic dishes aren't. The blank margherita canvas practically offers itself to being topped with a slice of salami or ham or anchovies.

Which is fine – variety is the spice of yadda yadda yadda... But the past few months have seen an egregious wave of deathly toppings making their way into the mainstream pizza market.

Part of this charge is led by a man who really ought to know better. Jamie Oliver's Union Jacks chain – which debuted in St Giles, London, last year – has reinvented the pizza as a "flat" and switched mozzarella and sauce for "Anglo" delights such as pork shoulder and Stilton. Why hast thou forsaken us, Jamie? Perhaps it's long-awaited revenge for that moment in Jamie's Italy, when the chef – frustrated by his Apulian hosts' inability to withstand the slightest experimentation with their local food – wishes that Italians were more open-minded.

Is the "Old Spot flat" his vengeful comeback? Of course Jamie's having the last laugh, though – new branches of Union Jacks have just been announced in Bluewater and Winchester.

Jamie may argue that his flats aren't a bastardised pizza at all, but a brand-new invention. Fair enough. But, if we give him the benefit of the doubt, then we absolutely can't do the same for some of Britain's best-known food brands whose new toppings make Jamie's Union Jacks look like Naples' legendary pizzeria Michele...

Marks & Spencer infamously launched an English Breakfast pizza to "celebrate" the Queen's Diamond Jubilee back in February. Its combination of Cumberland sausage, mushrooms and brown sauce proving barely good enough to throw at the royals in republican protest, let alone a celebratory feast. Meanwhile, the chain Fire & Stone offers a near-smorgasbord of baffling toppings, from guacamole on its "Mexico City" creation to the "New Delhi" with spiced Indian chicken and yoghurt (yoghurt!). Another, the "Buffalo", offers roast potatoes.

London delivery chain Deliverance – which offers such takeaway options as Irish stew and sushi – has just announced that chef Benny Peverelli (ex-Leon) has created three new pizzas for them – one with chicken and truffle oil (something the peasants of Naples obviously used to pelt on their pizzas) and another with a sauce-free base but topped with crème fraîche, smoked salmon and dill. The idea of smoked salmon on a pizza (though not a first) ought to have the pizza makers of Naples filing class-action lawsuits.

But is the fundamentalist approach of Neapolitans, who eschew everything but sauce, cheese and dough, too strict? Should we embrace the anarchy of bastard pizzas combos?

Thom Elliot thinks pizza creators should sit somewhere in between. Thom and his brother James went on a pilgrimage to Italy to learn the fundamentals of great pizza before launching the Napoli-inspired Pizza Pilgrims – which they now serve daily from their travelling van/oven at London's Berwick Street market. Elliot believes that experimentation in pizza is good. But to a point.

"We do [adhere to the Neapolitan rules] where we think it's necessary," he tells me. "In Naples it's literally like a religion, if your pizza is not made with the right flour or the right tomatoes, cheese and oven at the right temperature –they don't count it as pizza."

But for Elliot, who laments toppings such as chicken tikka – a less fundamentalist approach to experimentation is preferable: "Having this rule of not being able to put anything else on it ridiculous. In Rome we met a guy who makes pizza al taglio, big sheets you buy by weight. His philosophy is the exact opposite – good quality ingredients for the base – but he puts anything on to see what works. He claims never to have made the same pizza twice."

Which seems as good a pizza philosophy as any. As long as your base pizza is made with the good stuff – you're welcome to put whatever you like on it. But if it's yoghurt or roast potatoes, don't blame us when we vote with our feet.