It was actually Alec Walker.
Sally Wainwright's (author) mother's husband.
Where the idea of Last Tango came from?
It says on the website;
It’s my mum’s story; this happened to my mum. My dad (Harry Wainwright) died in 2001, and my mum (Dorothy) came to live with us in Oxfordshire, in our granny flat. My sister helped her put her details on Friends Reunited, and she discovered just two people there from her year at school (in Elland, West Yorkshire). One of them was Alec Walker. He was also widowed, and living with his daughter in Northamptonshire. They started writing to one another, and then he asked if she’d like to meet up. They fell in love with one another, and got married within six months.
Source(s):
http://www.bbc.co.uk/mediacentre/mediapacks/tango/writer.html