The Silver Cloak was a group of pensioners which Wilfred Mott was a part of.
After Donna Noble visited the Library, (Silence in the Library / Forest of the Dead) she decided to return home for a while. Upon arriving home and asking her mum where gramps was, Sylvia told her he was with those "silver surfers or whatever they called themselves". (AUDIO: Prequel (Donna Noble: Kidnapped!))
In one occasion, Wilf set them up to find the Tenth Doctor, as he believed the Doctor could help his granddaughter Donna remember him. The group travelled in a Sparrow Lane minibus, and talked via walkie-talkies. On Christmas Eve 2009, they found the Doctor in two hours. They took a picture with him, and then left for Wilf to speak privately with the Doctor. The Doctor was surprised they found him so quickly, remarking it took centuries for most people to find him. (TV: The End of Time)