Xavier and Xander are a pair of diesels that are permanently coupled together.
Xavier and Xander were brought to Sodor to help with heavy goods trains.
Xavier and Xander are based on a BR Class 13. The type was designed in 1965 because of the need to provide more powerful shunters for the Tinsley Marshalling Yard. Because of Tinsley's status as a hump yard, it was not possible to use a single locomotive owing to the risk of grounding. So, to achieve the required power, a pair of Class 08 shunters were permanently coupled in 'master and slave' formation, with the slave unit having had its cab removed. Only 3 Class 13s were built and all 3 were scrapped
Xavier and Xander are painted in BR Rail Blue with yellow and black warning strips on their backs. Their number, 13004 is painted on Xander's cab sides in white. They also both have their names on their sides in white.