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The extreme sport of BASE jumping has come under increased scrutiny as at least five people have died in accidents since January, including two last week at Yosemite National Park.

BASE stands for "building, antenna, span and earth" - the types of places from which jumpers leap.

So what is the appeal? Professional rock climber and BASE jumper Leo Houlding said: “It’s extremely exciting – to take a running jump off a cliff that’s three quarters of a mile high, accelerate from 0 to 120 miles an hour in the first 9 seconds and then plummet towards the earth.

“It’s very exciting and exhilarating - the reason it’s so exciting is because it’s so dangerous."