Imagine. You have invented a gun that has revolutionised the armaments industry. The world’s navies are buying your steamships as fast as you can build them. And, to cap it all, your mastery of hydraulics has made you a power in the land. In short, you are so wealthy, and so patently self-made, that future generations will describe you as a Victorian Bill Gates. Time, then, to build that Wagnerian fantasy palace you always dreamed of - the one with the mullioned windows and half-timbered gables.

William Armstrong already owned a modest mansion on the edge of the Cheviot Hills when he decided to realise his dream. So he had the Scottish architect Norman Shaw transform it into a stately pleasure dome while he and his amateur botanist wife Margaret set to work on the grounds - all 1,000 acres of them. There is no doubt that they could have bought themselves an off-the-peg park befitting their station. But Armstrong was an inventor, an engineer, a man who made things. And what he made out of the once barren acres at Cragside was a picnicker’s paradise.

Does the idea of the man who armed both sides in the American Civil War lolling on a tartan rug and nibbling cucumber sandwiches seem a bit hard to stomach? Perhaps it is. But there can be no doubt that among the steady stream of high-ranking visitors who passed through his lavish guest suites in the course of a year, there would have been many who regarded dining al fresco as an essential ingredient of a civilised lifestyle. For this was the heyday of the picnic - the moment when the English, and even the occasional Scot such as Armstrong, made it something peculiarly their own.

The word “picnic” originated in the 17th century, and combined the French words piquer, meaning to pick or peck, with nique, denoting something small and of little value. In the early days, a piquer-nique was a fashionable gathering where each guest would contribute something to the fare. At the beginning of the 19th century, members of the Picnic Society dined at the Pantheon in Oxford Street, drawing lots to decide who would bring which part of the meal, while in The Mystery Of Edwin Drood, Charles Dickens noted that Miss Twinkleton only “contributed herself and a veal pie to a picnic”. But as the railways made it possible for Victorians to travel into all but the farthest flung of rural parts, the chief characteristic of the picnic became its outdoor setting, with the burden of provision now falling squarely on the shoulders of the host. Or more accurately, on those of the host’s servants. And you don’t have to take more than a peek at Mrs Beeton’s Book Of Household Management to understand just how many servants and how broad the shoulders. For among the upper echelons of society, the High Victorian picnic bore a striking resemblance to a military operation.

According to Mrs B, writing in 1861, a party of 40 would require a joint of cold roast beef and another of cold boiled beef, a couple of ribs of lamb, two lamb shoulders, four roasted fowls, a pair of roasted ducks, a ham, a tongue, two veal and ham pies, a couple of pigeon pies, half a dozen medium lobsters, a piece of collared calf’s head, 18 lettuces, six baskets of salad and an equal number of cucumbers. Recommended desserts included “stewed fruit well sweetened, and put into glass bottles well corked”, along with an alarming assortment of turnovers, puddings, blancmanges, puffs, rolls, sponges and biscuits. Just washing this lot down would require half a pound of tea (“Coffee is not suitable for a picnic, being difficult to make”), as well as ale, soda water, lemonade, sherry, claret, champagne, brandy - and, of course, lashings of ginger beer.

The one thing that Mrs Beeton omits, but which would almost certainly be included in any modern-day picnic hamper, is water, which she points out “can usually be obtained; so it is useless to take it”.

Transporting this food and drink, together with all the paraphernalia that we associate with indoor dining, would have been a logistical nightmare.

But at Cragside, which is now a National Trust property, Lord Armstrong’s inventiveness went some way to lightening the load. Not only did he transform the rocky moorland of his estate into a Himalayan landscape by planting seven million trees and shrubs and creating a series of lakes, he also included in his scheme three carriage rides, each encircling the property at a different level.

“We think that probably guests were taken out in the carriages, dropped at a suitable point where they could have a picnic and enjoy a spectacular vista, and then have a leisurely stroll down these beautifully stone flagged paths back to the house again,” says Pam Dryden, Cragside’s learning and interpretation officer. “The lowest ride is six miles round, and there are viewpoints along the way. It would all have been very genteel, and the carriage would have done all the hard work.” According to etiquette manuals of the day, gentlemen picnickers were required to consider the fragility of the ladies at all times, taking care to avoid excessively dramatic locations, exposure to strong sunlight and, of course, anthills.

The playing of outdoor musical instruments was encouraged at Victorian picnics (this was an ideal opportunity to give the cornet an airing), and the playing of outdoor games (croquet, blind man’s buff and tag) was all part of the fun. And at 5 o’clock sharp, tea would be taken, and the servants would pack up for the journey home. Blind man’s buff? Lord Armstrong? It’s not impossible. But at Cragside, the first house in the world to be lit by hydroelectricity, one tends to think of the engineer leading small parties of guests on lakeside forays where they could marvel at the workings of his various dams and dynamos. He was, after all, the Bill Gates of his day. And you don’t get to scale those dizzy heights by lolling around on a rug all day.