Frederick was born on 5 October 1844 in Frankfurt, Germany. He was educated at Rugby school, Warwickshire entering the school in 1859. The headmaster at the time was Frederick Temple.
Frederic Mainwaring's father died in 1862. Frederic emigrated to New Zealand in 1864 with his brothers Eugene (1841-1911) and Randolph (1839-1902). For the first few years the three brothers were pastoralists on the Manipouri Station, south-west Otago, in the south of New Zealand. This was unprofitable. Randolph became a journalist. Eugene, who had trained as an engineer, joined the New Zealand Public Works Department. When Ashburton County Council was formed in 1878, Frederic joined as a clerk. (Ashburton is 50 miles south-west of Christchurch.)
Frederic was an excellent employee. He served the council for 44 years without a day's leave until early May 1922 when he was granted twelve months sick leave. He died only a fortnight later.
|Ashburton County Clerk, New Zealand Press, 6 May 1922 page 9 retrieved from PapersPast|
|Obituary New Zealand Press 19 May 1922 page 10 retrieved from PapersPast|
Ashburton Council was authorised by legislation (section 56 of Reserves and other Lands Disposal and Public Bodies Empowering Act 1922Public Act 1922 No 50 Date of assent 31 October 1922) to
pay to Adelaide Mainwaring, widow of the late Frederic Mainwaring, formerly Clerk of the said County Council, a sum not exceeding one hundred and fifty pounds by way of compassionate allowance.Frederic had married Adelaide Sarah Blundell (1856-1945) in 1874. They had two daughters, one of whom died in infancy.