A former paratrooper is isolating on a usually uninhabited Shetland island after lockdown measures were introduced when he was on a fundraising challenge to walk the UK coastline.

Chris Lewis, 39, has walked 12,000 miles since setting off from Llangennith beach on the Gower peninsula near his home city of Swansea, south Wales, in August 2017.

He was sleeping in a tent on mainland Shetland when the government announced the introduction of lockdown measures on 23 March to limit the spread of coronavirus.

Lewis and his dog, Jet, travelled by boat to Hildasay, a 108-hectare island off the west coast of the Shetland mainland, and have remained there ever since.

They have been given permission to live in the one house on Hildasay, a former shepherd’s hut without running water, heating or electricity.

Once the lockdown is lifted, Lewis and Jet intend to continue their journey around the UK coastline to raise money for SSAFA, the armed forces charity. Donations have already reached almost £98,000.

Lewis and Jet are staying in a former shepherd’s hut without running water, heating or electricity. Photograph: Chris Lewis/PA

“I’ve mainly been in isolation for the past two years due to the nature of the places we’ve been walking,” Lewis said. “When I heard there was going to be a lockdown, I was kindly given a boat to get over to Hildasay, which is an uninhabited island. I thought it would be better if I wasn’t on the mainland; I didn’t want to be in the way.

“There is one house on the island and the family of the man that used to live there heard I was camping and offered me the keys. Everybody is in isolation at the moment – it’s the one thing I can do. This will be over for me when it’s over for everyone else.”

Coal, water and food are brought over by boat when the weather allows. The items are left on the island’s pier, and Lewis then walks the 600 metres from the house to retrieve them.

Lewis collects driftwood, forages and fishes for his food, and always makes sure he has a three-week supply of dog food for Jet.

Hildasay has been uninhabited since the late 19th century, Besides Lewis and Jet, there are 15 sheep and thousands of birds.

“It has really given me a chance to enjoy the island,” Lewis said. “I’m able to reflect on the walk so far, just realising what this has done to help me personally and the amount of amazing people there are in the UK. I’m the happiest I’ve ever been.”

Lewis says he keeps a three-week supply of dog food for Jet. Photograph: Chris Lewis/PA

Almost 40,000 people have been following Lewis’s journey on a Facebook page, Chris Walks the UK.

Lewis said he struggled to cope after leaving the Parachute Regiment and finding himself homeless. He slept on the street and in cars before SSAFA stepped in to help.

“I came out of the forces and I was a single parent,” he said. “I suffered badly with anxiety and depression. At the time, I wasn’t speaking to anyone. SSAFA showed me there were people out there that were going to be there for me. Their support was so personal.”

When he faced homelessness for a second time, he set off from Llangennith beach on the Gower peninsula with £10 in his pocket and a few days of supplies.

When he is able to resume his fundraising challenge, Lewis will make his way to the north of Scotland before heading down the east coast of the UK.

“I’m looking forward to being out on the road again and being around people too,” he said. “I’ve learned that it was isolation that fixed me. You have to look at it in a very positive way. You have to make the best of it.”