Shirley is no longer the newbie on the judging panel however, as it was announced last month Motsi, 38, would be replacing Dame Darcey Bussell, 50.
Motsi’s appointment has received some criticism from fans of the show as she is the sister of professional dancer, Oti Mabuse, 29.
Ahead of her debut on the panel next month, Len has offered some advice as well as words of warning to Motsi about how best to approach the backlash she is likely to receive.
Speaking about the predicament Motsi will face when she is put in the position of judging Oti in the bottom two, Len told The Sun it will be the “harder thing” the new panelist will have to experience.
“Whatever decision she makes Motsi will get criticism. If she puts Oti through then people will say she’s doing her sister a favour,” he explained.
“If she votes her off they will say she didn’t want to be seen to be keeping it in the family,” Len continued.
Warning the newbie over the backlash, Len said: “All you can do is make the decision based on what you see and try to act with integrity.
“I’m sure Motsi will do that and if that means having to vote Oti off then that’s what she’ll have to do.”
Oti previously spoke out about working with her sister on Let’s Dance Germany where Motsi served as a judge on the panel.
Former Coronation Street star Catherine Tyldesley, 35, took to Twitter to post: “London bound… it may involve sequins…”
Comedian Chris Ramsey, 33, also wrote on the micro-blogging site on Wednesday: “First day filming stuff for @bbcstrictly today!
“Filming done @bbcstrictly. Did the interview stuff and the daft messing about with glitter balls and things….
“Didn’t feel as much of a tool as I thought I would! GREAT SUCCESS!”
With the interview segments used in the coupling up show seemingly done and dusted, it will only be a matter of time before fans learn when Strictly will return.