I don’t want to know what made Mona Lisa smile but wonder furiously about the picnickers’ menu in Manet’s Déjeuner sur l’herbe. It matters. If it didn’t, the artist could have omitted the food, like Cézanne in rendering the same subject. Bread and fruit are visible: all painters seem to have thought them essential picnic fare.

There is also an enigmatically covered dish. What nakedness does it conceal? I shall never know, but I can make suggestions, if not about Manet’s models, who, it seems, had more than a meal in mind, then at least about what the ingredients of summer picnics ought to be.

As well as a lavish menu, crockery, glassware and napery must make no concessions to practicality: practicality is the aesthetic of the savage

There are conditions more important than ingredients, and ingredients more important than food. First, you must be free to choose glorious weather and an unfrequented site. In England, people picnic at the command of sporting authorities, country-house opera impresarios or educational establishments that condemn families to cramped, sodden and hurried displays of annual competitive invention. If you picnic where others might see you, you have chosen the wrong spot.

In the most famous English fictional picnic, Ratty and Mole, like Manet’s bathers, favoured a riverside, where heavy comestibles can arrive by boat, with bottles cooled by trailing in the water. The excursionists in Emma, who had servants to carry everything, preferred the only other admissible location: a hilltop, blessed with a grand view, “pigeon pies and cold lamb”.

They omitted, however, the most important ingredient of all: good company. In consequence the heroine experienced “a morning more abhorred in recollection than any she had ever passed”.

Ratty’s menu had the cardinal virtue of excess. Cold chicken requires, at least, the supplements of “coldtonguecoldhamcoldbeefpickledgherkinssaladfrenchrollscresssandwiches pottedmeatgingerbeerlemonadesodawater —.” But he complained of his own abstinence — rightly in one respect, since champagne is the only acceptable summer picnic drink.

As well as a lavish menu, crockery, glassware and napery must make no concessions to practicality: practicality is the aesthetic of the savage. Let the civilised rejoice in pomp, circumstance, reckless expense and conspicuous consumption. A boat makes picnicking all too easy and, to boaters, rivers are unadventurously familiar.

So let us, with Emma, head for the hill. The picnicker’s generally unresolved dilemma is how, without the added encumbrance of intrusive servants, to haul the caboodle upslope. No compromise is admissible on the weight of champagne and the coolants it requires. So savings of weight must be made elsewhere, without loss of luxury.

Avoid sandwiches. Even Ratty’s, of cress, or the game sandwiches drooled over by Bingo Little, or the caviar-filled triangles that feature in Women in Love are liable to curl or harden by the end of the climb. Anything in a jar or flask is a waste of weight. Cutlery is unnecessary, though toothpicks are light enough to carry for impaling quails’ eggs or anchovy-stuffed olives, which go well together. Plastic containers cheapen and desecrate.

Victuals that gain nothing from exposure to plein air include slabs of cheese of unwieldy gravity, salads that sadden in the sun, and anything with an unalluring skeleton or wrapping that must be cleared away. Exclude them.

Dressed crabs and lobsters, much as I love them, generate depressing and demanding mess. Scallop shells, by contrast (which cushion all seafood with dignity), nestle comfortably amid the champagne on the outward route, and are rationally removable for re-use. The best container is the pastry that enfolds foie gras or small fillets of rare beef coated in truffled terrine.

Almost anything benefits from being baked in a pie. Choux buns can be filled with savoury concoctions or sweet creams. Vegetables stout enough to support encircling films of smoked trout or jamón ibérico include asparagus, lady’s fingers, and tiny carrots or baby maize-cobs.

Bread is indispensable, but must be crusty, airy and of the kind you tear. You can steep it in cheeses that come in precious, light wooden boxes and turn pungently deliquescent in the English summer. Berries in paniers are insuperable and sightly. Liquorous griottes in chocolate, stoned in every sense, are a complete post-picnic cordial, as long as the boxes they come in are too beautiful to discard.

I have never had such a picnic, nor any of which I approve, combining the sybaritism of unrestrained indulgence with ease in serving and clearing. Excursions unspoiled by rain and wind have been wrecked by tiresome playing fields and carparks and vexatious picnickers, boorish or braying, who populate them. The tedium of carting away a lot of unaesthetic detritus has ruined the fun.

The worst effect of the English habit of gathering for outdoor feasts is that it encourages joyless one-upmanship: luxury is morally acceptable, and therefore thoroughly enjoyable, only unostentatiously, in the discretion of privacy. Simplicity beckons; for everyone recalls the most romantic literary picnic of all: jug of wine, loaf of bread, thou and wilderness.