We can all agree (well, we hope so) that pie is a good thing. That, in whichever form it arrives, it's likely to be comforting and delicious. From the weird and wonderful regional pies found all around the UK (a slice of Stargazy, anyone?) to universal classics like beef and ale, the quintessential British pie is a thing of beauty, a classic on restaurant and pub menus and a nostalgic favourite in homes. But what is less easily agreed upon is what, exactly, a pie is. Does it need to be fully encased in pastry to count, or does a filling with a pastry lid do the job? What about dishes that have adopted the name, but are topped with everything from potato to meringue? Then there's the world of hand-held varieties like pasties, pork pies and sausage rolls – and we haven't even considered tarts.

Perhaps before we tackle such important issues we should set the scene. The history of pies in the UK dates back centuries; they've been a part of our cuisine for a remarkably long time, since at least the Roman period. But before we discovered the delights of rich, buttery pastry, pies were primarily practical, with the pastry acting as a vessel for preserving meat. During the Medieval period, pies became popular among the upper classes, often filled with meats like venison, rabbit and various bird, served as the centrepieces of lavish feasts and banquets. It was throughout the sixteenth and seventeenth centuries that pies became more accessible to the wider population and throughout the Victorian era they became a staple of working class diets in particular (it’s around this time that classic London pie, mash and jellied eels came to be).

Today, while pies are a symbol of classic comfort food, they are also elevated by some of the country’s top chefs, many of whom will have different ideas of when a pie stops being just that. So, getting back to the vital matter at hand, let's begin at the least contentious end of the scale. Few would disagree with the most purist of pie definitions; a filling which sits in a pastry base and is topped with a pastry lid. The British Pie Awards, for example, limits its entries to meats and fruits 'wholly encased in pastry'; lattice, fruit or potato-topped pies are left out in the cold, along with the likes of samosas. During our comprehensive research on all things pastry, we stumbled on some more obscure requirements from some corners of the pie world (including that pie must be made of shortcrust pastry and rules around how big any holes in the pastry can be – we take a pretty flexible view on both of those), but we're happy to agree that, as a general starting point, anything with a pastry base and topping firmly counts as a pie.

Opinions become entirely more divided when we ditch the base. A pastry lid appears to be a pretty agreed-upon pie staple; removing it entirely creates a tart, or flan, and though we're big fans of shepherd's pie and cottage pie, replacing pastry with spuds does seem to to chip away at its pie status (that's our definitive ruling on that). But what about a filling simply topped with a pastry lid, or a pot pie, as its more commonly known in America? Mary Berry waded into the debate a few years ago on Britain's Best Home Cook, when she said she 'wouldn't put pastry underneath' her chicken pie – something her fellow judge Dan Doherty disagreed with, succinctly describing a pie without a base as 'a stew with a hat on'. It's hard to deny that, for home cooks in particular, pot pies are quicker, more fool-proof and usually as delicious as their with-base counterparts. Oisin Rogers, landlord of London's The Devonshire, agrees. 'This pedantry about a pie having to have a pastry base is rubbish,' he agrees. 'Pies have been made in vessels with pastry lids forever. In fact, originally the pastry was inedible and just for holding the delicious contents. Football pies need bases because you have to invariably eat them standing up at half time with no table. Pies are great, a stew with a pastry lid is a pie. Definitely.'

Decisive stuff. We're sold. But what about handheld varieties? If traditionalists are keen to define pies as a filling encased in pastry, why wouldn't a sausage roll or Cornish pasty count? It comes down, they argue, to the lack of structure – rather that just being covered with a single sheet of pastry, a typical pie has a base, sides and lid (or at least elements of the above), and two distinct pieces which are generally joined in the making of the pie. That's what Anna Søgaard, head chef at Bistro Freddie, believes. 'I would personally consider pasties and sausage rolls to be pastries and not pies,' she nods. 'It's the pie dish and lid that classifies it as a pie.' The British Pie Awards, however, does include categories for pork pies and Cornish pasties, slightly muddying the waters. We're torn, but are tempted to err on the side of pasties being, well, pasties. 

Whether you agree or disagree with where we think the definition lies, ultimately, it doesn't really matter – whatever its structure or finished look, the likelihood is that it will be tasty, and we know that's what really matters. We asked Oisin to sum up why he thinks pies have such an enduring appeal. 'They're easy to eat by design,' Oisin nods, 'and any delicious thing can go in the filling, like oysters with beef, anchovies with lamb, tarragon or curry sauce with chicken. The crust is a vehicle for the flavours and the goodness and adds all the texture. They are the best invention. Long live the pie, in all its forms; a good balanced one is pure perfection.' Hear, hear.