Winston Churchill was Prime Minister during World War 2
Winston Churchill appeared first in the second episode of the series calling the Doctor. He wanted help but in his room a shadow of a Dalek appeared this meant trouble.
When the Doctor arrived in World War 2 London to see Churchill, Churchill wanted the Tardis key so that he could use the Tardis to win the war. Winston had other weapons including 2 new ones which destoryed a group of Nazi Spitfires. They were called Ironsides but they were actually Daleks. The Doctor knew they were up to something and they were. They wanted to make a new Dalek race with the last surviving Dalek Saucer behind the moon. A Progenitor was on board which made the new Daleks 100% pure Dalek. Winston Churchill realised they were dangerous and sent in some Spitfires to help the Doctor destroy the Daleks laser beam. After disarming a bomb on Earth the Doctor left but almost without his Tardis key. Winston took it from him but Amy noticed that he did.
He later appeared with a painting by Vincent Van Gigh with a picture of the Tardis being blown up. Winston called Professor River Song and asked what was it about? She didn't understand but she knew somewhere where she could get it from.
Winston made a third appearence as Emperor of Britain as time was rearranged. Romans were still living, Silurians living with the human race and Buckingham Palace was a Roman shrine. Winston wanted his sayer the Doctor to tell him what happened to time as he noticed it had stopped. He stayed with the Doctor until the Doctor was taken by River's guards including one of them who was Amy Pond. Winston was confused but later returned to his own time of World War 2 London.
He has appeared in:
Series 5: Victory of the Daleks and The Pandorica Opens
Series 6 Part 2: The Wedding of River Song