On 15 November, Barker and his pilot, flying very low over the Ancre River, spotted a large concentration of German troops massing for a counter-attack on Beaumont Hamel.

[9] In January 1917, after spending Christmas on leave in London, he commenced pilot training at Netheravon, Wiltshire, flying solo after 55 minutes of dual instruction.

On 25 April 1917 during the Arras Offensive, Barker, flying an R.E.8 with observer Lt. Goodfellow, spotted over 1,000 German troops sheltering in support trenches.

[11] On 7 November 1917, 28 Squadron was transferred to Italy with Barker temporarily in command; most of the unit, including aircraft, travelled by train to Milan.

[14] Owing to his tendency to ignore orders by flying many unofficial patrols, Barker was passed over when the post of Commanding Officer of 28 Squadron became vacant.

He carried out an unusual sortie on the night of 9 August when he flew a Savoia-Pomilio SP.4 bomber to land a spy behind enemy lines.

The poor upward visibility of the Camel resulted in Barker cutting away progressively larger portions of the centre-section fabric.

[15] Having flown more than 900 combat hours in two and a half years, Barker was transferred back to the UK in September 1918 to command the fighter training school at Hounslow Heath Aerodrome.

He attacked an enemy Rumpler two-seater which broke up, its crew escaping by parachute (the aircraft was of FAA 227, Observer Lt. Oskar Wattenburg killed).

Severely wounded and bleeding profusely, Barker force-landed inside Allied lines, his life being saved by the men of an RAF Kite Balloon Section who transported him to a field dressing station.

A possible related casualty was Jasta 24 Vfw Schymik, killed in action, while Barker may have been shot down by Js 24's Ostv Friedrich Altemeier.

[21] The Overseas Military Forces of Canada recognized Barker as "holding the record for fighting decorations" awarded in the First World War.

A plaque on his tomb in the mausoleum of Toronto's Mount Pleasant Cemetery, officially unveiled on 22 September 2011, describes him as "The most decorated war hero in the history of Canada, the British Empire, and the Commonwealth of Nations".

[23] Barker formed a business partnership, Bishop-Barker Aeroplanes Limited, with fellow Victoria Cross recipient and Canadian ace Billy Bishop which lasted for about three years.

[24] Barker was appointed acting director of the RCAF in early 1924 and he graduated from RAF Staff College, Andover, England, in 1926.

He formally reported on his findings to the Minister of National Defence, and informally to Brigadier General Billy Mitchell, of the US Air Service.

After leaving the RCAF he became the first president of the Toronto Maple Leafs hockey club and was involved in tobacco-growing farms in southwestern Ontario.

He died in 1930 when he lost control of his Fairchild KR-21 biplane trainer during a demonstration flight for the RCAF, at Air Station Rockcliffe, near Ottawa, Ontario.

The cortège stretched for more than a mile and a half, and it included the Chief of the General Staff and his senior officers, the Lieutenant Governor of Ontario, the Mayor of Toronto, three federal government cabinet ministers, and six other Victoria Cross recipients.

Some 50,000 spectators lined the streets of Toronto en route to Mount Pleasant Cemetery, where Barker was entombed in his wife's family crypt at the Mausoleum.

The Discovery Channel's Flightpath series, a television documentary, included an episode entitled "First of the Few", a biography of Barker, which was broadcast on 27 April 1999 in Canada.

A memorial at Mount Pleasant Cemetery in Toronto was unveiled on 22 September 2011 to mark Barker as the "most decorated war hero in the history of Canada, the British Empire, and the Commonwealth of Nations.