In 1761 Summergrove was sold by Anthony Grayson to James Spedding (1720-88), the son of Carlisle Spedding, a famous mining engineer and agent to Sir James Lowther. James married Elizabeth Harrington (1745-1821) and their son James (1779-1863) was a captain of the 1st Foot Guards and Major in the Royal Westmorland Militia.
His son James Dykes Spedding (1810-1851) married the Hon Emily Wyndham and their son James Wyndham Harrington Percy Spedding (1849-1924) inherited. This James died without issue in Capri in 1924 and Summergrove passed to his cousin Mark Quayle. In 1931 the estate was sold to Quayle's relative John Anthony Spedding (1878-1940) of Storms, Keswick. This John had a son Charles Spedding (1907-61) but I do not know if he lived at Summergrove.
In Cumberland Families and Heraldry, from which this information is taken, under Spedding of Summergrove there is listed Joseph Carlisle Harrington Spedding (1905-??) who had a son John Carlisle Spedding (1951-).