He was born in
Lewisham in southeast London on 3 April 1879, the son of Richard Barnwell, a director of the
Clyde shipbuilder
Fairfield. Barnwell was brought up at Elcho House in
Balfron,
Stirlingshire, and educated at
Fettes College in
Edinburgh. He had a younger brother,
Frank. Frank and Harold Barnwell built their first
glider in 1905 in Balfron and later built three powered aircraft. They then opened the Grampian Engineering and Motor Company in 1906 at Causewayhead in
Stirling. From their garage, they produced three aircraft between 1908 and 1910. The first was underpowered and failed to fly, but the second, a
canard biplane was successfully flown from a field in Causewayhead under the
Wallace Monument on 28 July 1909. Piloted by Harold, it only flew 80 yards (75 m) at an altitude of about four metres before it crashed, but it is still recognised as
Scotland's first powered flight. Next, the brothers built a
monoplane with which Harold won a prize of £50 offered by the Scottish Aeronautical Society for the first flight of more than a mile to be made in Scotland in January 1911. In 1911 both brothers moved to
England, and in 1912 Harold, after gaining his pilot's licence (No.278) at the
Bristol school at
Brooklands in September joined the staff of the new Vickers School of Flying, also at Brooklands. Here he was the instructor who helped
Noel Pemberton Billing win his £50 bet with
Frederick Handley Page by learning to fly and gaining a pilot's licence in a single day. In late 1914, Harold Barnwell, now chief
test pilot with
Vickers Limited, designed a single seat "scout" or fast reconnaissance aircraft, and had it built without the knowledge or approval of his employers, "borrowing" a
Gnome Monosoupape rotary engine from Vickers' stores to power the aircraft. Barnwell attempted the first flight of his design, named the "Barnwell Bullet" in early 1915, but the aircraft crashed and was wrecked, possibly due to a miscalculated
centre of gravity. ==Death, memorial and legacy==