Gordon Davidson

 was Rachel Zimmerman's younger brother. He had an artificial hip, replaced after his old hip was shattered by a bullet, and underwent physiotherapy for a long time afterwards.

As a former CID operative, he was put in charge of security at a party thrown by Rachel and her husband Nick Zimmerman. This party would become trapped in a time loop, repeating for long enough to erode the walls of its reality against the time vortex.

When the Eighth Doctor and Lucie Miller arrived one day he asked to see their invitations. He said that meeting Lucie felt like the first new event to happen in ages. Gordon would later help the Doctor fight the Tar-Modowks and ride a vortisaur. (AUDIO: No More Lies)