As compliments go, being compared with a giant, gas-filled 300ft long, 143ft-wide ‘flying bum’ cannot rank highly on most women’s wish lists.

But as the airship Martha Gwyn inched its way out of an enormous green hangar for the first time, the soubriquet seemed anything but blimpish.

Named after the wife of businessman Philip Gwyn, yesterday’s (Saturday) public unveiling represented a milestone in a £350million project that had once appeared doomed to remain grounded.