The start of the asparagus season was greeted like the birth of a child – and the end like a death in the family. In all honesty, I’m not sure my Granny ever really found any joy in cooking her own food and lived on cheese and biscuits. When I spoke to other middle-class girls with posh grannies, we discovered we had much in common.

One former private chef to a member of the Royal family described knowing when the late Queen was joining his client for lunch as he would receive instructions to make a single serving of “goujons of plaice, which are basically posh fish fingers, because no matter what everyone else was having she really did prefer plain food”. And aside from a few crusty old dukes, you don’t get much posher than the Queen, do you?

So what are the signs of a truly posh diet and how can it benefit your health?

You never snack

A weekend guest at Lisnavagh, the seat of Lord Rathdonnell, describes their host’s visceral disgust at snacking: “He considered it a punishable offence, completely gross and abject gluttony.” Admittedly, snacking was not common to any class until more recent generations were brainwashed by food companies. As a child, whining that one was hungry was either ignored or met with a brisk: “You can have a piece of fruit.”

And while we all chew away all day like cattle at the cud today, it remains strictly not done in the grandest echelons of society for its simple lack of restraint and self-control. And there is nothing to eat anyway. One regular visitor to the nice country houses says upper-class fridges are singularly uninspiring. Fresh ingredients are kept in the larder to be prepared from scratch and “snacky bits” are what Nancy Mitford would call “non-U” (not upper class). “It’s just dried up ends of cheese, sad, worryingly bloody chicken carcasses and Tracklements mustard.” In short, if you open your fridge and a cornucopia of exotic foodstuffs sheathed in brightly coloured plastic tumble out, you’re dead common.

Nutritionist and functional medicine practitioner Rosemary Ferguson is a favourite of the smart set in London and the Cotswolds. She says: “Not snacking is a good thing. The body benefits from short fasts of around five hours between meals. So snacking is a really big issue because insulin levels are elevated all the time and the body never takes a break from digestion.”

You love high-protein game

As a rule, to shoot things with faces, fur and feathers legally you need to either own a lot of land, have a friend who owns a lot of land or be prepared to give someone with a lot of land a lot of your money. Otherwise it’s poaching. Having a taste for the gamier meats is a sign you are quite grand. Arrivistes just shoot the things and go off to Annabel’s to get drunk.

Ferguson says: “Game is very healthy meat: high in protein, low in fat, rich in B vitamins, vital minerals like iron and omega-3s. It lives wild and is probably not living a stressed life on lots of weird foods and medications like farmed meat.”

You avoid UPFs like Bisto gravy or (horror) a Big Mac

While there are rumours the Beckhams enjoy Bisto with their very finest quality beef, the act of roasting a few ribs of beef requires only the addition of stock to the empty pan to create a fairly thin yet deliciously marmite-y liquid called gravy. A travelling companion of one of the smart Sykes sisters – Plum, Lucy and Alice – describes an unnamed sister preferring to go hungry for 24 hours while waiting for a delayed flight at Goa Airport because the only option was McDonald’s and, apparently, she “just couldn’t”.

Ferguson says: “Cooking from scratch and avoiding UPFs and fast food is a very good thing, however, I’m afraid I love Bisto. I remember [a very aristocratic name] being audibly appalled when they discovered I did. The real problem comes when you don’t have the choice. Diabetes and metabolic illnesses are a socioeconomic issue because in poorer areas there are food deserts where UPFs and fast food are cheaper than real food. So it’s no laughing matter.”

You prefer plain food with good quality ingredients

While Pol Roger claimed Winston Churchill drank 42,000 bottles of its champagne over 50 years, his menus were far less grand. “They included a lot of leftovers and beans on toast,” according to dining historian and biographer of Churchill’s cook Dr Annie Gray. “It is the same now as it always has been,” she says of the upper-crust predilection for plain and unexciting food.

Ferguson says: “Keeping it simple means consistent habits; anything too complicated is easily derailed. And if you are eating good quality ingredients, quite often too much fuss really isn’t necessary.”

You eat strictly seasonal vegetables

It would never cross your mind to eat asparagus, artichokes or tomatoes, or indeed, anything, out of the strictly British season for them, and certainly not pre-prepared in a crackly plastic packet. Sliced carrots should never be seen outside the nursery wing. Adults’ carrots should be served in batons or peeled and left whole according to both Annabel Bower’s Mancroft instructions and etiquette commentator William Hanson. And some vegetables are completely verboten. “Kale is for cattle” according to my mother. She has never stopped saying this since I developed a fashionable appetite for the toughest of brassicas. No matter how much I gussy it up or massage it to tenderness, she will not touch it. A member of the Mancroft family, apparently, sent a swede dish back to Bower with the words: “You can’t serve that. That’s cattle feed.”

Ferguson says: “Seasonal, local and freshly picked or dug is the dream. As soon as they’re picked, vegetables start to lose their nutritional value and flavour. And if pulled from organic garden soil, there’s added minerals and good bacteria. Carrots cooked whole lose less of their nutrients to the boiling water; not peeling them would increase fibre and preserve nutrients even more. On the matter of kale, I’m clearly very common. I love it. It is nutrient dense and while some controversial and extreme wellness figures have claimed kale is ‘trying to kill you’, the truth is you’d have to eat a lot before we could pretend the plant’s protective toxins, known as oxalates, might be bad for you.”

You aren’t big on pudding but love fresh fruit from the garden

Crumbles with loads of cream brought to the kitchen daily direct from one of the dairy farms on your vast estate are also acceptable. Ferguson says: “A crumble isn’t bad at all, with the fruit, and especially if you add some seeds, nuts and oats. The addition of local and unpasteurised cream (that has been tested for food-borne pathogens) will add high-dose vitamin E, high A2 protein and fat levels to keep you satiated for longer.”

You never salt food before you have tasted it

One friend describes gasping in horror when she realised the man she loved sprinkled salt all over his food before he’d even had a mouthful. “I’d been told to salt food was very non-U, and I still like my food bland to this day. I was told salt could sit in a little pile on your plate to be used if necessary but that sprinkling was a giant no-no. Ferguson says: “Unless you’ve had an arduous day in the garden, when you might allow yourself a little pinch of salt to restore good electrolyte balance after sweating – sorry, perspiring – we should all be avoiding salt. We all eat way too much and it is a well-known and serious risk factor for cardiovascular, kidney and bone health.”

You only drink very weak tea (and never with sugar)

Taken with a slice or lemon or a droplet of milk, tea should look like dishwater, not the thick orange colour of a common house brick. Ferguson says: “This is probably more hydrating, perhaps, than stronger tea but as long as your tea isn’t full of sugar, there is nothing wrong with a strong daily cup of builder’s. You take it as strong as you like, I’m sure the etiquette police have better things to do.”