What's it like to be an undercover cop?

An undercover UK police officer used his fake identity to deceive a woman into a 19-year relationship in which they became partners and had a child together, according to British media. Mark van Leewarden is a former undercover cop in New Zealand, and was a member of Auckland's criminal underbelly for a year, gathering intelligence and trying not to get found out. Mark joins Nights to talk about the UK case, his former life as an undercover cop, and how he became New Zealand's most successful international fraud investigator.