Winston Katusi was an elderly Londoner living in the early 21st century.
Biography
Winston was a friend of Wilfred Mott and a member of the Silver Cloak whom Wilf sent out to find the the Tenth Doctor. Winston, Wilf and the other members used a mini-bus to follow the Doctor's movements. They located him in the wastelands of London and Winston joined the others in posing for a photo with the Doctor. Winston and the other members dropped off Wilf and the Doctor at a coffee shop before driving away.
Later, the Master activated the Immortality Gate to superimpose himself onto the entire human race. Winston telephoned Wilf just before transforming into a version of the Master. The Master's actions were later undone by Rassilon and Winston reverted to being human. (DW: The End of Time)