Brits Dave and Kevin Keylock. Dave: "I always dreamed of having our own [restaurant]. But normal start-up costs are way too high."

Picture this: your picnic blanket laid out on the grass, plates of savory smoked salmon on flatbread, accompanied by sour cream, lemon, and potato salad, plus beer-battered fish and chips, spiced ground lamb on salad leaves, raita (the salty, minty Indian yogurt), and naan Indian bread. For dessert, the Queen Mother’s favorite: Eton Mess, a strawberry compote with crumbled meringue and fresh mint.

And you’ve just gotten this from a…food truck?

You betcha. Blanket included. Pretty soon, we might be taking tiffin, the afternoon tea-and-scones tradition dear to the Brits.

Again, from a food truck?

Welcome to the brainchild of Dave and Kevin Keylock, two brothers I’ve been trying to catch up with for a month. They discovered San Diego after a snowboarding vacation in Colorado a couple of years ago. (They came here afterward, to warm their tootsies, and decided that this was where they wanted to live and work.) Kevin is a business major, while Dave is a chef who cooked for a few months for Queen Elizabeth (yes, the Jubilee gal herself) at Buckingham Palace. Which has to be where they got the idea for the name of their San Diego food truck: “God Save the Cuisine.”

Locating them hasn’t been easy. By the time I find their red truck inside the gated apartment complex of Archstone in Mission Valley, I feel like Henry Morton Stanley, the American journalist-explorer who found Dr. David Livingstone in the African jungle.

So, okay, in the wilds of the San Diego river valley, I come up to these two lanky guys.

They’re wearing red T-shirts with a message: “Keep Calm and Eat Well.”

Veddy English.

“Doctors Livingstone, I presume?” I say. Well, actually, what I say is: “Dave? Kevin?”

Their red truck looks like a cross between a London bus and a UPS van. And, right now, the guys look beat.

“This has been our busiest day, ever,” Kevin says. “It’s incredible. Everybody seems to have come out of their apartments. And each one is buying for two or three others. We completely ran out of things like our spiced lamb on naan.”

Naan? He shows me the item on the menu, written on chalkboard and set on a sidewalk stand.

“It’s the Indian influence back home,” says Dave. “Spiced lamb on an Indian flatbread — naan — is popular there. People seem to be liking it here, too.”

Fish and chips is their most popular item, and after that, the spiced lamb, Indian-style.

Most things on the board are pretty English, like the banger, broccoli from the griddle, and chips (“fries,” it explains), for $7. Except, hey, there’re fish-and-chip tacos ($8) — two tacos with “local beer-battered fish, with homemade coleslaw and tartar sauce and malt vinegar and salt for the truck-cut chips (fries).”

“We do want to adapt to some local customs,” says Dave.

Then they have smoked salmon on flatbread ($9) and pear salad ($7). Plus a dessert: organic strawberries ($4).

I’m looking at the board, trying to decide.

“Usually we have a bigger selection,” Kevin says.

Turns out, the only two items left after tonight’s rush are the smoked salmon and your basic fish and chips — not in tacos. That’s fine by me. Which one should I get? What the heck, why not order both. I’m thinking of taking the salmon home to Carla.

Ten minutes later, the freshly battered fish comes out steaming, sitting on top of this little Indian flatbread loaded with coleslaw and arugula and radish slices. Tartar sauce sits on top. Then lots of fries, and three little plastic pots, one filled with vinegar, one with sea salt, one with ketchup. Plus a slice of lemon.

I’m glad to have that interesting naan instead of tacos. With the coleslaw and arugula, it’s different and refreshing.

I leave the salmon for the lovely Carla to open later. Well, that’s not quite true: I do have a quick look, and, okay, a quick bite. Beautiful pink slices with sour cream on top, naan underneath, with arugula and — and this is great — tangy capers scattered around.

This is when somebody I’d noticed moving about in the truck comes outside. Lani, Dave’s American wife. “I really taught them how to cook,” she says.

She’s kidding, of course. She met Dave while he and Kevin were on that snowboarding trip in Colorado. Before that, Dave had been at culinary school in the UK; he ended up being chosen to apprentice at Buckingham Palace. “My favorite member of the family?” he says. “The Queen Mum. She was the funniest person there. She’d chase off people who wanted to help her walk, when she was getting a little frail. We loved her.”

So, is this a comedown? Food truck, way out West, after the palace?

“Absolutely not. I always dreamed of having our own place, but normal start-up costs are way too high. This food-truck phenomenon makes it possible. We find ourselves at the cutting edge. It gives us a learning curve and the chance to experiment.”

Like, serving up streetside roast-beef dinners, with Yorkshire pudding and horseradish and watercress. Scones and strawberries and cream. “We’re thinking of doing our version of Taco Tuesdays. Ours will be ‘Tea Tuesdays,’” Dave says. “Afternoon tea on the roadside.”

Now I notice all the plaid rugs, rolled up below the counter for easy grabbing.

“These are for people to spread on the grass by the truck. Make a picnic of it. We English love spontaneous picnics.”

In the end, I have the last of their strawberries and cream ($4), “just the way the Queen Mum loved them,” with fresh mint leaves and hand-whipped — almost clotted — cream.

I bet Prince Charles, the nature farmer, would love them, too. These are organic, from Suzie’s Farm in IB. The guys say they’re sourcing everything from right here in ’Diego.

Dave says gastro-trucks aren’t really happening in England yet. “Maybe we should do that some time,” he says. “Take Californian food to the streets of London.”

Oh, yeah. I can just see him and Kevin and Lani driving their food truck straight into his old gig, Buckingham Palace, and calling out in the great Cockney tradition, “Tacos! Vegan burgers! Grunion fritters! Fit for a queen!”