[5] He disappeared in April 1912 while attempting to fly from Holyhead, Wales, to Ireland in a Blériot monoplane, and was presumed dead shortly after.

[2] The following week, on 26 April, Vivian Hewitt successfully completed a flight between Holyhead and Dublin, landing in the Phoenix Park.

Interviewed by the press, he expressed the view that Allen had been insufficiently experienced as an aviator for a flight of such difficulty.

[10] At the time of his death, Allen was being sued in the English courts for the recovery of a portrait of Lady Anne Ponsonby[11] by Thomas Gainsborough,[12] which he had sold at Christie's for 8,300 guineas (£8,715).

On 11 February 1913, after a seven-day trial, the jury returned a verdict for the defendants, including the executors of Allen's will.