Actress Jenna-Louise Coleman was impressed by the high levels of secrecy surrounding Doctor Who after her role was given a code name to throw off fans.
Producers used the phrase Men On Waves when auditioning actresses to replace Karen Gillan as Time Lord Matt Smith's assistant - but Coleman managed to crack the code.
She tells the Radio Times, "I worked out that Men On Waves is an anagram of Woman Seven, because this is the seventh series (since the show re-launched in 2005). Weirdly, seven is my lucky number and this is my seventh job."
The former British soap opera star was also banned from discussing the high-profile TV role with family and friends until she was officially unveiled as the newest addition to the cast.
She adds, "I wasn't allowed to say it was Doctor Who at any point - not talking to my agent, not when I arrived at the audition, and I certainly couldn't tell anyone at all what I was up to next."