Karl Bushby has conquered jungles, deserts, a frozen sea and the Kremlin’s visa office, all on foot. But his hardest journey may be when he walks back through his mom’s front door.

The 57-year-old former British paratrooper is roughly 250 miles from finishing the Goliath Expedition, a 28-year odyssey that kicked off at the bottom of South America in 1998.

When he left, he had an 8-year-old son at home. That boy is now 36, a dad himself — and still waiting.

Is Bushby ready to face his adult son nearly 30 years after starting his Odyssey?

“Well, that’s gonna be a tough one,” Bushby told The Post when he called from London. “[I am] looking forward to reconnecting with everyone. There’s distance between us, and we need to patch that up, and move on.”

His son Adam, who lives in Belfast, told the Yorkshire Post that his father’s homecoming “doesn’t seem real.”

But it got a lot more real on Oct. 5.

That afternoon, Bushby dragged himself out of the surf at Shakespeare Beach just south of Dover after logging about 20 hours in the water over three days. His father and brothers were waiting on the sand. It was the first time he’d set foot in Britain since the Clinton administration.

He kept the swim under wraps until he was safely ashore, clearing it in advance with French and British officials and both countries’ coast guards.

Not bad for a guy who once admitted he swims “like a cat dropped in a bathtub.”

Bushby had originally lobbied to hike through the Channel Tunnel’s service passage, but the operator shot him down, leaving him no choice but to get wet.

“It feels good to have UK soil under my feet after all these years,” he told The Post in a separate statement. “It hasn’t been easy, and that’s part of the point.”

A bet gone very long

Bushby spent 12 years in the 3rd Battalion of the Parachute Regiment before quitting the army at the end of 1997. He was reeling from a bitter divorce and itching to prove himself.

“I had something to prove to my paratrooper mates,” he told Backpacker magazine.

Before making the trek, Bushby forged two ironclad rules: He could never use a vehicle to go forward, and he couldn’t go home until he walked there.

On Nov. 1, 1998, he set out from Punta Arenas, Chile, reportedly with less than $1,000 to his name. He marched the length of South America, hacked through the lawless Darien Gap into Central America and kept going until he hit Alaska.

In 2006, he became one of the first people to cross the frozen Bering Strait on foot, hopping between drifting ice floes and paddling through open water into Siberia.

The harsh truths of nature wouldn’t stop him — but boring, maddening bureaucracy would.

Visa fights stalled Bushby in Russia for years, and Moscow slapped him with a five-year entry ban in 2013. He rerouted through Mongolia and China, swam for weeks across the Caspian Sea to Baku and Azerbaijan, finally reaching Europe last year. By June he was in Belgium, staring down the last big obstacle between him and Hull.

No regrets

Asked to name the toughest leg, Bushby didn’t hesitate.

“Lots of different hard parts, but let’s say the Darien Gap and Alaska,” he told The Post.

His favorite terrain was in South America, especially Colombia, Chile and its bone-dry Atacama Desert. Picking a single highlight from nearly three decades proved impossible.

“I couldn’t say just one. There’s just a long list,” he said, ticking off the triumphs of escaping the treacherous swamps of Panama, landing safely in Russia, washing up exhausted near Baku and, now, hitting the beaches of Dover.

Despite tens of thousands of miles, Bushby insists his body held up fine thanks to a slow and steady pace.

“It’s kept me in shape,” he said. “There are some aches and pains, but anyone who’s gonna be 57 and above, and is physically active, is probably gonna be the same.”

And if he could do it all over again?

“It worked, so no, I wouldn’t change a thing,” he told The Post.

Back in Hull, his mother Angela has seen her son exactly three times since he left. She’s kept the whole saga in scrapbooks inside the Sutton Park house where he first pitched the plan — the same home he hasn’t entered since 1998.

“Karl has always been headstrong,” she told the BBC.

He’ll arrive with cameras rolling.

Legendary filmmaker Werner Herzog greeted him in Dover and is directing a feature documentary called “Walk of Life.” It’s being produced by Westward Productions, co-founded by “House of Cards” creator Beau Willimon and Jordan Tappis, alongside Skellig Rock and The Roots.

Westward has bankrolled and supported the trek for the past 16 years and archived his footage.

What comes next

Bushby is expected to reach his mom’s doorstep in late October or early November. After that, he admits, life gets murky.

“Mixed emotions,” he said of nearing the end. “We need to find another mission, another passion and get busy. That’s the solution, I believe.”

He plans to throw himself into the film and public speaking. And after nearly three decades of strangers feeding him, sheltering him and steering him safely to his next destination, he says the biggest lesson isn’t about grit.

“People are amazing, despite what we think the world looks like,” Bushby said. “Humanity is worth the effort.”

Now he has to prove it to the people who were waiting at home the whole time.