Philippa, better known as Pip, and Emma are two diesel-electric locomotives which make up a BR HST InterCity 125 train set.
Pip and Emma are based on the British Rail Class 43 HST. This engine holds the world record for fastest rail speed for a Diesel: 238 km/h or 148 mph.
Pip and Emma are painted in the original InterCity 125 livery of yellow and blue. After they were bought by the Fat Controller, the words "InterCity 125" and the BR logo which were painted on Emma's sides were replaced by "NWR". Emma also has a red and gold nameplate. At the start of Thomas and His Friends Pip is seen wearing her old BR guise, it is unclear as to whether or not she eventually had these replaced by the letters "NWR", or if she later received a nameplate.