@Maersk.146 These are preserved and have approval to run on the mainline. These are returning back to there home depot at Butterley having been to diesel galas at Severn Valley Railway and West Somerset Railway. There are operators that use diesel locos from the BR days class 37 is the popular one they have the nick name of tractors. Here's a Youtube video of a pair of DRS 37's leaving Swindon station on a rail tour the drivers really like to put on a good performance. https://youtube.com/user/ltspadman
https://youtube.com/user/ltspadman