The 22,500t HMS Ocean is similar to some of the smaller LHD designs like the 21,300t French Mistral Class. Built to commercial standards, LPH01/ L12 carries a crew of 255, an aircrew of 206, and 480 Royal Marine Commandos; an additional 320 marines can be accommodated in a short-term emergency. The ship has capacity for 40 vehicles, but its 4 Landing Craft Vehicle Personnel (LCVP) Mk 5s aren’t designed to handle heavy vehicles like tanks. Its main assets are up to 18 helicopters: usually 12 transport (EH101 Merlins or H-3 Sea Kings), and 6 smaller maritime/ scout/ attack helicopters (multi-role Lynx variants, and/or WAH-64D Apache attack helicopters). H-47 Chinooks can be refueled and serviced on deck.
HMS Ocean’s primary role is as an amphibious support vessel. Secondary ship roles include training, a limited anti-submarine warfare role, humanitarian assistance, and acting as a base for anti-terrorist operations. The 2011 campaign over Libya added a strike carrier role of sorts, using the WAH-64D. Those kinds of events have forced the ship to remain at sea near more distant shores, and on longer voyages, than originally anticipated. Hence the priority on crew-related modifications. Not to mention some of the other changes being made under recent refits.