Following on Panzer's thread on actors portraying US presidents, I am curious who best portrayed British Prime Ministers?

Being only a movie fan and not a Brit, I can only go by who I liked on screen, so I am very curious for suggestions.

My favorite so far is Gary Oldman as Churchill. Of course, he's not the only PM.
and Ian Richardson as Francis Urquhart (not real of course).

Recommendations?

My top 3 that I have seen either on film or a tv series:

1. Brendan Gleeson as Churchill in "Into the Storm".

2. Meryl Streep as Thatcher in "The Iron Lady".

3. Michael Sheen as Tony Blair in "The Queen"

Streep was excellent as Maggie, despite the outrage here generated by an American playing such an iconic English figure! Much better than the cartoonish characterisation by Gillian Anderson in a later production.
Sheen captured well the smarmy insincerity of Blair.

I wasn't impressed by Gillian Anderson as Thatcher either. She played her too rigid and brittle even.
I have to re watch Streep's portrayal.