Working boats

This is one of the more unusual vessels I have seen travelling down the estuary.  The boat in front is  the "Sarah Gray", described by marinetraffic.com as a "work boat" en route from Falmouth to Holyhead.  I'm not sure why it was here in the Severn estuary, nor could I find any description of the interesting vessel it was towing.

Just another day of activity on the estuary.