Some details of the Field-Hart family:
Margaret Patricia eldest of three surviving daus (a fourth recorded at birth as 'female'; the book by Lucy Irvine mentioned below gives 'three') of Kenneth Edward Field-Hart (1894-1940), of Hayes Court, Hayes, Middx., and (The) Limberlost, Heathfield, Sussex, poultry farmer, sometime of Connecticut, U.S.A., emp. Christian Science Monitor -1935 (at Boston, MA, then the London office), by his wife (m. 1916) Dorothy May, dau. of Davis. Their third daughter, Diana (1921-2003) was a Vogue model and furniture-maker whose marriage to- and life in the Solomon Islands with- Thomas Andrew Cradock Hepworth (1910-1994), son of the filmmaker Cecil Milton Hepworth, was the subject of a book ('Faraway') by Lucy Irvine (also author of 'Castaway' etc).
K. E. Field-Hart only s. (also a dau., Gwendolen Mary Field-Hart) of Edward Hart (1857-), of 18, Carlisle Road, Hove, Sussex, formerly of Epsom, Surrey, and of Devonshire Road, Lewisham, chartered accountant, and his wife (m. 1880) Ellen Alice (1858-1910), née Field [b. Southwark; possibly dau. of Owen Field, of Russell Court, Whitechapel]
Edward Hart eldest s. of Edward Hart (1828-), of Highbury, Islington, formerly of Knockholt (n.b. Knockholt doesn't appear to be near enough to Swanscombe for this Knockholt to be 'in' Swanscombe; perhaps this was the name of his house? The census record has 'Knockholt' under 'residence'), Swanscombe, formerly of Greenhithe, Dartford, Kent, chartered accountant, and his wife (m. 1854) Elizabeth, dau. of Thomas Tibbetts [/Tibletts; the second son was William Tibbetts Hart, b. 1859, a lawyer, which would indicate the former spelling, but the marriage record gives the second version of the name].
Edward Hart fourth s. of William Hart (1795-), of Herbert Street, formerly of Paul Street, Shoreditch, Middx., 'accountant to a public company', and his wife Elizabeth (given their eldest son's name, 'William Austin Hart', I considered it not unlikely that she was originally surnamed 'Austin', but couldn't locate a matching marriage record). This William was born at Hatfield; a record at that location suggests his parents could have been William Hart and Esther, but there are several records matching the general area so this cannot be established easily.