Before he became an MP, Riddick worked for 10 years in various sales management roles with Procter & Gamble (1977–82) and Coca-Cola Schweppes Beverages (1982–87).
In July 1994, a "sting operation" by The Sunday Times implicated Riddick in the "Cash for Questions" affair.
Both Riddick and fellow Conservative MP David Tredinnick were accused of accepting cash for asking questions.
When The Sunday Times reported the story Riddick immediately apologised to Parliament but was subsequently found to be in breach of Parliamentary rules and was suspended for 10 days.
He contested his seat again at the 1997 general election, but lost to the Labour Party's Kali Mountford, who won with a majority of 4,840.