A grandfather who became the oldest person to row 3,000 miles unassisted across the Atlantic Ocean has encouraged older people to “keep active and challenge yourself”.

Frank Rothwell, 70, from Oldham, set off from Canary Island La Gomera on December 12 and crossed the finish line in Antigua in the Caribbean on Saturday – reuniting with Judith, his wife of 50 years, with time to spare until Valentine’s Day.

The achievement has also raised more than £720,000 for dementia research with Alzheimer’s Research UK.

The adventurer has previously spent five weeks on a deserted island for a Bear Grylls TV programme, and rowed solo in a boat nicknamed Never Too Old.

“I think a lot of us older people don’t use our skills to do things with hobbies,” Mr Rothwell told the PA news agency.

“They should think of something that’s difficult to do… it may be they’re physically restricted, but do something that will challenge you.

“That will extend your life – an interest, something to get up for in the morning.

“When I get home from here I’m building a six-tonne steam traction engine from scratch in my garage… I can’t wait to get started.

“Judith is really happy because she said ‘that’ll keep you anchored at home for a while’.”

Despite his age, Mr Rothwell came fourth out of eight solo boats that took part in the Talisker Whisky Atlantic Challenge.

He said most participants’ boats worked on a basis of two hours of rowing and two hours sleeping, but he treated the task like a normal day.

“I’d start in the morning as it came light,” Mr Rothwell said.

“Because of the cramped conditions on the boat it would take me an hour and a half to actually get up brush my teeth, take my tablets, make my breakfast… make sure I phoned everybody up.

“Part of my condition of going out here was that I would phone Judith every day.”

After breakfast, Mr Rothwell would generally then row in two or three-hour stints, with 10 or 20 minute breaks in between and breaks for meals – finishing the day’s rowing when darkness fell.

“It was hard, I can’t imagine anything being as difficult as this,” he added.

“It is quite easy to die… if you fall over the side and you’re not hooked on you’re dead – there’s no two ways about it.”

Mr Rothwell said that every week or so he would jump into the sea wearing a safety belt so he could scrape barnacles off the bottom of the boat to aid its speed.

When he eventually arrived at the finish line two months after setting off, Mr Rothwell said the feeling was “euphoric”.

“That’s a really emotional bit that, it’s a special, special feeling,” he said.

“The place was filled with mega superyachts and they all hooted their horns. That was for me, it was fantastic.”

Mr Rothwell added that he was “proud” his family allowed him to take part in the race, as he had wanted to cross the Atlantic in a sailboat six years ago but they would not let him.

“I then become an old codger and go ‘can I row across the Atlantic single-handed?’ and they said ‘oh yeah you can do that’… it isn’t logical,” he laughed.

Mr Rothwell said the money raised for Alzheimer’s research was in tribute to his brother-in-law Roger Wheeldon, who died with the condition aged 62 during his row.

Mr Wheeldon also had Down’s syndrome and had been living in a care home for the last 30 years.

“It motivated me along and gave me time to reflect on Roger and his life,” Mr Rothwell said.

Mr Rothwell set out to raise £1 million for Alzheimer’s Research UK, and looks set to achieve this after Iceland Foods Charitable Foundation pledged to double the first £500,000 of his donations.

If you would like to help Mr Rothwell’s cause, you can donate at www.justgiving.com/fundraising/frankrothwell