None of the variants allowed in-flight arming of the fissile core. The core was inserted before take-off, in a process referred to as 'last minute loading'. For carrier-borne aircraft, landing with the armed weapon was forbidden, and the aircraft would instead be diverted to a shore airbase. Although the Royal Navy required its Sea Vixen aircraft to be type-approved for Red Beard carriage as 'insurance' against delays in the development of the Blackburn Buccaneer, the Sea Vixen never deployed in the nuclear strike role. Early models were subject to severe environmental limitations, especially when loaded into Royal Navy Scimitars on exposed aircraft carrier decks in Northern waters. The Mk.2 variants were better engineered to withstand extreme conditions, and other than the yield difference, this was the main area of difference.