The final part in the ‘Monk’ trilogy of episodes, The Lie of the Land, was reportedly set to contain a scene in which the world of Casualty makes reference to the Monk’s invasion of Earth, thereby tying the two universes together. In the scene, actors Amanda Mealing and Tony Marshall, portraying their Casualty characters, praise the Monks for saving someone in an accident, stating “Praise be to the benevolence of the Monks”. This all takes place in Casualty itself, cementing the show’s broadcast as part of Doctor Who‘s world.
It is unknown why the cameo was ultimately cut; perhaps it took away from the intended tension of the episode or simply couldn’t fit into the runtime, but whatever reason it may have been, it sees the BBC continuing to tie Doctor Who into greater parts of British culture, such as cameos by real-life presenters and personalities like Hue Edwards and Brian Cox in series past.
Source: Digital Spy