Arnold Plackett was born in Breaston, Derbyshire, England on 18 March 1887. He studied at Nottingham University and was articled to Ernest Hooley (1880-1962) in Long Eaton, Derbyshire. By 1910 Plackett had commenced practice as an independent architect. He was a Member of the Society of Architects and was admitted a Licentiate of the Royal Institute of British Architects (LRIBA) in 1925
His address was given as Central Chambers, Long Eaton in c.1910; Imperial Buildings, 11, Derby Road, Long Eaton in 1923 and 1926; and Imperial Buildings, 15, Derby Road, Long Eaton in 1939. Plackett retired from practice in 1959 and died in Ilkeston, Derbyshire on 3 June 1960.
Architectural projects by Placket included 149 Wollaton Road, Beeston, Nottingham (1914); 11 Devonshire Avenue, Beeston, Nottingham (1923); 13 Devonshire Avenue, Beeston, Nottingham (1925); four shops, 118-124 High Road, Beeston, Nottingham (1928); 10 Marlborough Road, Beeston, Nottingham (1929); houses, Holden Road, Beeston, Nottingham (1934); 28 Houses, Off Muriel Road, Beeston, Nottingham (1935); houses, Endsleigh Gardens, Beeston, Nottingham (1935); houses, Charnwood Avenue and Larch Crescent, Beeston, Nottingham (1936); 12 Bramcote Avenue, Beeston, Nottingham (1936); 1 Cumberland Avenue, Beeston, Nottingham (1936); 63 Humber Road, Beeston (1936); Manor Farm Estate, High Road, Toton, Nottinghamshire (1939-40); extensions to W. Reynolds and Co.'s works, Watnall Road, Hucknall, Nottinghamshire (1948). Plackett also designed several lace factories and a cotton spinning mill; a large number of bungalows; and worked on the development and lay-out of several estates ranging in size from 50 to 100 acres.