Their Helicon Double Layer Thruster uses radio waves to ionise one of the inert, or noble gases - a group which includes krypton, xenon and argon.

BBC: Glow from argon plasma. Image: LPTP, Ecole Polytechnique

Further proof came in another story making waves in Strasbourg, the departure of British Conservatives from the main centre-right group, the European People's Party (EPP).

ECONOMIST: Charlemagne