[5] Merton's first significant science-fiction credit was as Ping-Cho in the 1964 Doctor Who story Marco Polo,[8] long since lost in its original form.

In 1999, Merton reprised this role in the short film Message from Moonbase Alpha, written by series writer Johnny Byrne.

Its debut was at the closing ceremony of the Breakaway 1999 convention[9] in Los Angeles, California, US on 13 September 1999; the date on which the moon is blasted out of Earth orbit in the pilot episode of the original series.

Following Space: 1999, Merton appeared in many popular television series including Grange Hill,[2] Return of the Saint (1979),[2] Bergerac (1983),[2] Angels (1983),[2] Tenko (1984),[2] Dempsey & Makepeace (1985),[2] Lovejoy (1986),[2] Crime Traveller (1997), Doctors (2001),[2] Dinotopia (2002), Casualty (1986–2002),[2] EastEnders (1998–2003),[2] The Bill (1999–2005),[2] Judge John Deed (2006), Coronation Street (2008)[2] and Wire in the Blood (2008).

In December 2008, Merton filmed a guest role for the eighth episode ("Samaritan") of the ITV drama Law & Order: UK.