Former England rugby international Mike Tindall is gearing up for what is billed as Scotland's toughest one-day endurance event.

Tindall, 36, will be among 300 competitors in the Artemis Great Kindrochit Quadrathlon - a 1.35km swim in Loch Tay followed by a 24km run, an 11km kayak and a 54km cycle.

He will be partnered by ex-Scottish international scrum half Rory Lawson and will compete against British skiing champions Chemmy Alcott and Dougie Crawford.

The gruelling event on Saturday July 11 is expected to raise £250,000 for charities Mary's Meals and Mercy Corps.

Tindall said: "Since retiring from rugby it's good to challenge yourself in different ways, but the panic is setting in a bit now.

"The biggest challenge for me is definitely the run. It's over seven Munros, so it could be an issue.

"Rory's 20kg lighter than me and better at running. He's not the best swimmer, so I said I'll wait for him after the swim if he waits for me after the run.

"I think if we can do it in 12 to 13 hours then we'll be over the moon."

The quadrathlon, now in its 15th year, has previously been won by Perthshire-based adventurer and round-the-world cyclist Mark Beaumont who completed it in eight hours 37 minutes.

On reaching the finish line, each team must chop a watermelon in half with a sword.

Tindall, who is to married Zara Phillips, said his wife plans to be there to cheer him on.

He has been training for the event since appearing as a contestant in the Channel 4 show The Jump and Bear Grylls: Mission Survive, shown on ITV earlier this year.

Tindall said: "I don't know if any of that has quite prepared me for the wilds of Scotland.

"We've been speaking to a few guys who've done it before - like (former Scotland rugby captain) Rob Wainwright - for advice.

"I've been doing stuff on the bike, a bit of cross-country and practising the distances for the swimming, but not outdoors in lakes or anything.

"We've done no kayaking, so that will be interesting."

The former Bath and Gloucester player, who was a member of the 2003 Rugby World Cup-winning squad, said he will enjoy being a spectator at this year's tournament, hosted by England from September 18 to October 31.

He said: "When you stop playing and you are watching, you think 'I could do that better' and so on. But I've passed that stage.

"I think England have got a really good chance. I think England are up there in terms of the depth of the players."

Tindall also said Scotland should not be too down-hearted after taking the wooden spoon in the RBS 6 Nations earlier this year.

He said: "I think Scotland are on a building process at the moment, they've had to restart things.

"But I think (Scotland coach) Vern Cotter is very good for them. I think they can be positive going forward."