Birdwatchers will tell you that it is important to keep an eye on your garden, as some interesting rarities can turn up.  I’d agree, have seen a yellow-browed warbler in ours a few years ago, and our neighbour saw a rose-coloured startling.

The same applies to trains (sometimes.)  Walking home over the railway bridge….

Allan informed me that it is a class 153, now used by the Network Rail inspection team.  An Wikipedia says.

The British Rail Class 153 Super Sprinter are single-coach diesel-hydraulic railcars which were converted from two-coach Class 155 diesel multiple units in the early 1990s. The class was intended for service on rural branch lines, either where passenger numbers do not justify longer trains or to boost the capacity on services with high passenger volume.

In May 2021, Network Rail purchased three units (153311, 153376, and 153385) for use on infrastructure monitoring services.

Looks like a typical modelling ‘cut-and-shut’ job.  I rather like these second generation ‘Sprinters’.  Sean also saw it at Horsham the day before.