The Doctor + consequences 2/?
'I thought I knew the name. Harriet Jones, future Prime Minister. Elected for three successive terms. The architect of Britain's Golden Age.'
Except Harriet never fulfills her three terms as remembered by Nine, as Ten deposes her and she is removed from office after a vote of no confidence. This rewriting of history gives the Master the opportunity to gain a foothold in the British government and be elected Prime Minister.