After the victory at Cape St Vincent on 14 February 1797, Sir John Jervis took the fleet into the Tagus at Lisbon to await reinforcements; a number of damaged ships or those needing maintenance, including Jervis's own flagship Victory, were sent home and Jervis transferred his flag into the brand-new Ville de Paris, the first 110-gun ship in the Navy and fresh from the builder's yard. Several weeks later, on 31 March, the newly-ennobled Lord St Vincent led his resupplied fleet of twenty-one sail back out to sea and set course for Cadiz where he intended first to blockade the port and then, in time, tempt the twenty-six remaining Spanish ships-of-the-line sheltering there out to fight.
After six weeks patrolling the coast, St Vincent established his close blockade on 19 May and anchored off the town in a crescent formation, with an Advanced or Inshore Squadron under Nelson close in the mouth of the harbour. Despite their numerical superiority however, the Spaniards refused to come out and, in early July, St Vincent decided to bombard the town in the hope of provoking a response. This too proved fruitless and, in the autumn, the fleet returned to the shelter of the Tagus leaving a small observation squadron to maintain the blockade through the winter.
The number of his extant paintings -- oils as well as watercolours -- dated between 1797 and 1800 suggests Buttersworth was producing a significant output whilst still in the naval service and his views of the battle of Cape St Vincent (14 February 1797) and, more numerously, those involving the activities of the blockading squadron off Cadiz indicate that Buttersworth witnessed these events in person:
'...the marine artist Thomas Buttersworth painted a number of watercolours of the ships of the Inshore Squadron around this time which show the Bellerophon anchored alongside the Theseus, Nelson's flagship. Buttersworth was a seaman on one of the ships in the main body of the fleet under Lord St Vincent and although his pictures are strangely lacking in atmosphere they are full of carefully observed detail. The anchored ships of Nelson's squadron are beautifully drawn; he notes the boats moored alongside their sterns, and the longboats and cutters coming and going in the foreground. His pictures clearly show how close the squadron was to Cadiz. According to Nelson, "We are looking at the ladies walking the walls and Mall of Cadiz and know of the ridicule they make of their sea officers".' (D. Cordingly, Billy Ruffian, The Bellerophon and the Downfall of Napoleon, The Biography of a Ship of the Line, 1782-1836, London, 2004, pp.111-12.)