Day of the Dinosaurs

If this evening's Dinosaurs on a Spaceship achieves nothing else, it will at least have laid to rest the ghost of previous dinosaur misfires in the series. Tonight's creatures are the work of The Mill, who handled the monsters for ITV's 'Primeval'. When producer Barry Letts was considering doing a dinosaur story in 1974, he was assured that it would be technically possible. Model dinosaurs could be placed in model settings, and would be able to interact with actors via CSO. The models would be realistic and manipulated utilising the same rod-operation / puppetry techniques which had proved successful with the Drashigs in Carnival of Monsters. Sadly, Letts was misinformed. Invasion of the Dinosaurs is a very good story now notoriously let down by its titular monsters.

Barry Letts: "Noooooooooooooooooooo!!!!!!!"

To be honest, its primarily the T-Rex which lets the side down. I watched this story again recently, and have identified only a couple of scenes where CGI replacements might have been difficult to insert.
When shown the CGI optional additions to The Time Warrior DVD release, Letts is said to have remarked "So what about those dinosaurs then...?"
Letts was no stranger to realising dinosaurs on screen in Doctor Who. One of his very first jobs was to furnish The Silurians with a monster. He decided that it should be a full size costume (of a dinosaur which matches no known creature in the fossil record). The costume was so heavy, the head had to be supported with an off-screen chain attached to a rig above the performer. The monster was then inlaid onto the action via CSO. Letts then had a "Doh!" moment when he realised he could have achieved exactly the same effect with a model / puppet in CSO.

The aforementioned Carnival of Monsters featured a Plesiosaur, which is only shown briefly a couple of times when it terrorises the S.S. Bernice..

The world's most famous Plesiosaur, that shy inhabitant of Loch Ness, appeared in Terror of the Zygons. "Nessie" was explained away as being a cyborg alien dinosaur. The sequences with the Doctor on the moors are quite well done - but the "glove-puppet" final appearance is woefully realised.

Doctor Who's other big dinosaur reference is in Earthshock. The TARDIS has landed in a cavern full of fossils and the fifth Doctor talks to Tegan and Nyssa about the possible demise of the dinosaurs - the result of an asteroid impact about 65 million years ago, which caused a "nuclear winter". He says that he has always meant to pop back and check. Of course, future events in this tale will show that it was an Earth freighter, with poor old Adric onboard, which will collide with the planet and lead to the destruction of the dinosaurs - and the eventual rise of we mammals.