The imminent onset of wintery conditions at the beginning of October 1764 required James Cook to end his survey of the Northern Peninsula of Newfoundland for the year, and begin the journey back to St. John’s. Before he left, however, and with Grenville anchored at Old Ferolle, Cook determined to complete the survey as far as Ferolle Point. On 1 October, the small boats set out from Grenville. One of the boats struck a ledge, causing it to bilge and fill. Fortunately, the cutter managed to save all of the boat’s crew.
Cook’s instructions required him to be back in St. John’s by the middle of the month, so he packed up, and began the return journey. Grenville sailed out past the Dog Peninsula on the afternoon of 5 October, and headed up the Strait of Belle Isle. At noon on the 9th they passed Groais Island. Cape Bonavista, the southeastern end of the “French Shore”, was rounded on the 11th. Two days later at 8pm, Cook anchored in St. John's Harbour.
Sir Hugh Palliser, Newfoundland’s Governor, gave permission for Cook to take Grenville back to Britain, so she was prepared for an Atlantic crossing. Cook had argued that the sloop could be repaired, and made ready, back in Britain during the winter, thereby saving valuable time for next summer’s survey. Four of the supernumeraries had been discharged back to their “proper ships” in St. John’s but the other six stayed to help man the sloop.
Grenville left on 1 November and, after a month’s crossing, anchored in the Catwater at Plymouth on 4 December. Leaving on the 7th, she reached Woolwich on 12 December. Finally, on the 20th, she tied up alongside the wharf at Deptford. Cook, possibly, left the vessel early to join his family in Shadwell, as Elizabeth gave birth to their second son, Nathaniel, on the 13th. With luck, Cook was at hand for the birth. Nathaniel was baptised on 8 January, 1765, at St Dunstan’s, Stepney, marking the beginning of the Cooks’ association with Mile End Old Town and Stepney.
Nathaniel’s baptism record shows that the boy was 26 days old when he was baptised.