Do you find this joke funny?

My friend has been obsessed with this joke which I find fairly boring and not funny. I wanted to see if anyone agrees/disagrees with me:

Three tortoises, Mick, Alan and Les, decide to go on a picnic. So Mick packs the picnic basket with beer and sandwiches. The trouble is the picnic site is ten miles away so it takes them ten days to get there.

When they get there Mick unpacks the food and beer. "OK Les Give me the bottle opener."

"I didn't bring it," says Les. "I thought you packed it."

Mick gets worried, He turns to Alan, "Did you bring the bottle opener??"

Naturally Alan didn't bring it. So they're stuck ten miles from Home without a bottle opener. Mick and Alan beg Les to go back for It, but he refuses as he says they will eat all the sandwiches.

After two hours, and after they have sworn on their tortoise Lives that they will not eat the sandwiches, he finally agrees. So Les sets off down the road at a steady pace.

Twenty days pass and he still isn't back and Mick and Alan are starving, but a promise is a promise.

Another five days and he still isn't back, but a promise is a promise. Finally they can't take it any longer so they take out a Sandwich each, and just as they are about to eat it, Les pops up from behind a rock and shouts........

"I KNEW IT!......I'M NOT GOING!"