and 2010. He was succeeded by Casualty executive producer Belinda Campbell. Casualty@Holby City Reflecting Holby City origins as a spin-off from Casualty and the closely related premises of the two programmes, the BBC has screened occasional crossover mini-dramas entitled Casualty@Holby City, featuring a number of characters from each of the two casts. Mervyn Watson, former executive producer of Casualty, has commented on the origins of the idea to fully cross the two shows over for the first time: "I think the idea came from somebody in the comedy department, who casually said to the Controller of Drama 'Wouldn't it be a good idea if ...' The Controller did think it was a good idea, spoke to myself and Holby's executive producer, got it commissioned by the Head of BBC One and the rest is history." Filming of Casualty@Holby City episodes is usually divided between Casualty's Bristol set, and Holby City Elstree studios, although a large proportion of the Christmas 2005 crossover was also filmed on location in a road tunnel in Caernarfon, Wales. The theme tune used for crossover episodes consists of a shortened version of both the Casualty and Holby City theme tunes, played over one another in sync, criticized by the Daily Mirror for being "basically both theme tunes played at once." Interviewed before the Christmas 2005 crossover was broadcast, Watson commented on the future of Casualty@Holby City: "We can't guarantee any crossovers for next year, but the audience likes them. And as long as the Controller of BBC One wants them, then we'll be happy to oblige." In November 2007, Holby City producer Diana Kyle added: "We like to do crossovers whenever we can, but it's tricky because both Holby City and Casualty film for 52 weeks a year, so the actors on each show have to work flat-out on their own programmes. We are trying to create more opportunities where the two dramas can merge, though." Another crossover was broadcast in 2010, with Casualty producer Oliver Kent commenting that the production teams enjoy airing crossovers, and that the difficulty in producing them is "purely logistics". HolbyBlue In April 2006, the BBC announced that a spin-off drama from the show, to be named HolbyBlue, was in early stages of production. The series focuses on the police service of Holby South, and aired for the duration of its first series on BBC One on Tuesday nights, with Holby