Although I was involved with the Basingstoke restoration, I was not involved with the dredging side.
In answer to Derek's query, I understood that the steam powered grab was used when the material to be dredged was hard and/or compacted and that the clam-shell grab (operated with chains and relied on gravity to dig down into the silt) was used when the material was soft. There were a number of times that the grabs were changed this was not something that happened very frequently. However, I understood that dredging using the steam-powered grab was slower.
Originally when she started dredging on the Basingstoke in 1975, the cabin on Perserverence was painted red but the colour was changed - can't remember when.
The film dates from the early 1990's. The opening shots of the tug were taken near Reading Road Bridge and the first shots of Perserverence show Pondtail bridge in the background. However, the film does not seem to have been compiled chronologically as later shots of Perserverence dredging are back nearer Reading Road Bridge.
When the dregings are shown being boated away, the tow is shown passing under Reading Road Bridge (very low), past a hire boat from Galleon Marine to the disposal site near Crookham Village west of Poulter's Bridge.
According to the Surrey & Hampshire Canal Society website: "In March 1993 Perseverance reached Pondtail Bridge, east of Fleet, and in October of that year, its work on the canal finished, it was taken by road to the Canal Museum at Ellesmere Port in Cheshire."
Peter