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Helium: Its role in the fight against cancer

Helium is the second most abundant element in the universe, but very rare on earth. Professor Andrea Sella of University College London explains to Justin Rowlatt the properties that make this inert gas so useful.

Another chemist, Peter Wothers, explains why he used a Christmas lecture to call for a ban on helium party balloons.

Our Washington correspondent, Jonny Dymond, is out in the wilds of the Texas Panhandle to explore the US National Helium Reserve.

And we hear from the head of General Electric's Magnetic Resonance Imaging division - one of the world's biggest users of helium - on why the gas is so important in the fight against many diseases.