4pm: This is how the Downing Street website is covering the visit:
"Former Prime Minister Margaret Thatcher returned to Downing Street today for private talks with Gordon Brown. Lady Thatcher was greeted with a warm handshake from the Prime Minister as she arrived outside Number 10 before the two headed off for a private meeting. During his press conference earlier this week, Mr Brown described Lady Thatcher as a "conviction politician" who "saw the need for change". Lady Thatcher was Prime Minister from 1979 to 1990."
4.45pm: The day gets more surreal...
Iain Dale phoning in to BBC News 24: "... isn't it great to see her back in Downing Street, back where she belongs?"
Presenter Sally Nugent bringing the conversation to an end: "It is."