cubitt was educated at trinity college, cambridge, where he graduated with first a ba and later took his honorary ma. he won election has a conservative mp for west surrey from 1860 to 1885, and then for epsom until 1892, when elevated to the lords as baron ashcombe, "of dorking, in the county of surrey and of bodiam castle, in the county of sussex", having been invested as a privy counsellor in 1880. he also served as honorary colonel of the 5th battalion, royal west surrey regiment, and deputy lieutenant of the counties of both surrey and middlesex.