There were three major modifications to this class in it first ten years - a move of the exhaust port, removeable roof panel bolt fixings replaced by clips, and conversion of 19 to push-pull operation, known as TOPS Class 33/1. Their main push-pull passenger operation was between Bournemouth and Weymouth, but at times they were also regularly used for push-pull services between Waterloo and Salisbury and Reading and Portsmouth. The other Crompton sub-class, the Hastings gauge/narrow bodied 33/2, was not represented at the Open Days.

On 33013 the "Swordfish" name is relatively recently applied.