Alison Bright-Thompson

Ms Bright-Thompson was the mother of Robin Bright-Thompson and the partner of Ken Bright-Thompson. While Ken and Robin lived in 107 Baker Street in 2020, she could not join them as she worked abroad. (AUDIO: Lost Property)

Later, Mr Bird called a residents' meeting in Baker Street, noting that "Mr and Mrs Bright-Thompson are out, as per usual". (AUDIO: Must-See TV)

Behind the scenes
In Lost Property, while citing the paperwork for the Bright-Thompsons' acquisition of a flat in Baker Street, Helen Sinclair refers to her as "Ms Bright-Thompson", while Must-See TV has Mr Bird referring to her as "Mrs Bright-Thompson". Which title she goes by isn't entirely clear; however, since the former is from an official document, it seems more likely to be the one.