Though the RN has never really gone in for more than one helicopter on a surface combatant; the Type 22s could in theory carry two Lynx, but AFAIK it wasn't really common practice.
There was at least one T45 deployment in the early days that had 2 Lynx onboard. I remember the photos of the hangar...there was more room than you'd think with them in.
Is it known why? Amphibious operations support?
T45 was designed to replace T42. The RN wanted to have a ship that took all the lessons from the Falklands, Gulf War and intervening periods baked in for once. These were things like:
- High radar placement for early detection of low level threats
- Large calibre gun that could leverage developments that others would pay for, that meant TMF 155mm. The idea was it wouldn't be an 'orphan' calibre like 4.5inch, and could leverage, at little to no cost to the RN, all the exciting developments in guided shells or carrier shells that were proposed at the time. It was pretty sensible in that regard....RN had also realised NGFS was still a thing...
- Lots of spare space, spare power, spare cooling for upgrades during the ships lifetime (RN had been stung heavily by costs to upgrade small Leander Class ships in living memory, and the T21's because of their inability to accept upgrades had effectively become obsolete within 10 years). The mantra here was 'steel is cheap, and air is free'....this also carried over into the CVF programme, and to a degree T26 (the large mission bay takes the concept far further).
- One of the Falklands lessons, and GW1, was that if you were going to have a helideck it made sense to have a size that would accommodate the largest RN helo on all vessels. No more Wasp or Lynx sized decks, with SeaKing having to stay onboard larger vessels. This meant from T23 onwards that all decks were and are 'Merlin capable', just decks initially, but all hangars built now are for Merlin as well. T45, due to the increased focus on 'Purple' i.e. Joint operations took this further by making the deck 'Chinook capable'. The largest helo in UK service. This also went along with the mantra of giving the ships room to grow for future systems as well. Type 26 and Type 31 also have Chinook capable decks as standard (the UK even did a study on powered blade fold for CH-47 at one point, but that was mainly for CVF).
- Additional accommodation for Embarked Military Force (EMF) and 'overflow' accommodation for additional personnel onboard above the usual complement (and the hotel services, galley space, storage etc to support). This was a lesson that could have been learnt at any point in the last 200 years...but the RN finally learnt it post Falklands...most ships since have included it, from River Class, T45, T26, T31 and CVF. T23 was a little too soon....turns out crew complements always grow...and in wartime you always carry more personnel than you thought you would...
- Massively upgraded accommodation for crew....this was with the realisation that modern recruits would just not accept the cramped quarters of before. Good accommodation meant better retention.....T45 is very much the gold standard, QE Class and T26 are very good, but apparently are not as 'luxurious' as T45 (and certainly nowhere near RFA's...),