Joan Hannington was a real life villain and member of the British criminal elite for over decade. She was indeed renowned as a diamond thief and did serve time in prison - but that was actually for cheque book fraud, not theft.
It typically takes two to three days to pass something swallowed through to your stools, and can't be hurried - so Joan would have to have lodged on the sofa for more than an evening, however much olive oil she consumed!
Episode 1, Joan in pub, Chris issac in background with Wicked Game. This episode is set in 1985. Wicked Game was released in 1989 in the USA, and 1990 in the UK.
Dedicated to Martin Maynard who worked in the Props Department during initial production of the series.
At the time the series is set a single unset diamond of reasonable quality would typically retail for up to £750 assuming they are one carat stones