Famous battles and famous ships.
The Brits always did that well, with battleships and ships of the line thus named (usually after a French defeat) Agincourt, Blenheim, Ramillies, Barfleur, Trafalgar, Nile, Camperdown, Waterloo, Quebec, Culloden and St Vincent. Interestingly, of the approximately eighty fleet, light and escort carriers operated by the Royal Navy, none was named after a battle.
Conversely, while royalty have ships named after them (HMS King George V, King Edward VII, Queen Elizabeth, Prince of Wales, Duke of York, etc), it very rare for the Royal Navy to name a vessel after a politician who had no meaningful military or naval career.
HMS Pitt is one rare example. So, I don't think we'll ever see a HMS Blair or Thatcher.
I wonder if the Admiralty would have made an exception for
HMS Churchill had the later Prime Minister not previously served with the Queen's Own Hussars from 1895, where he fought in India, Sudan and South Africa, including the
cavalry charge at Omdurman, and latterly on the Western Front during WWI where (after the Gallipoli disaster) he commanded a Battalion of the Royal Scots Fusiliers, leading 40 dangerous patrols into no-man's-land.
I expect not.