On Wednesday 26th April 1916, a Major Deasy contacted Guinness to see under what terms Guinness would allow the lorries requisitioned on the Monday to be converted to improvised armoured cars for use during the Easter Rising.
The only Major Deasy I can find is an Irishman by the name Henry Hugh Peter Deasy.
29th June 1866, born in Dublin.
20th April 1886, Lt in the 4th Royal Munster Fusiliers
10th November 1888, 2nd Lt in the 6th Lancers
29th January 1890, Lt in the 16th Lancers
17th February 1894, Captain in the 16th Lancers
1894, Fellow of the Royal Geographical Society
1896, exploration of Tibet
24th March 1897, resigns his Captaincy in the 16th Lancers
10th August 1897, Reserve of Officers
May 1900, note re his exploration work
August 1900, wrote article "Journeys in Central Asia"
1901, wrote "In Tibet and Chinese Turkistan" following 3 years of
exploration work
1903, founded H H P Deasy and Company Ltd, importing cars
1905, completed a 1000 mile motor trial around Ireland
1905, shareholder of the London Power Omnibus Company Limited
1906, founded Deasy Motor Car Manufacturing Company Limited (in 1912 it was to become
Siddeley-Deasy Motor Company Limited having been taken over by
John Davenport Siddeley)
11th October 1906, resigns as Chairman of London Power Omnibus Company Limited
22nd February 1907, winding up of H H P Deasy and Company Limited
24th June 1910, H P P Deasy and Company Limited accounts/liquidation
14th March 1911, Deasy Motor Car Manufacturing Company Limited
5th May 1915, Temporary Major, 8th Reserve Regiment of Cavalry
The
8th Reserve Regiment of Cavalry was formed in August 1914 and based in the Curragh. Affiliated to 16th and 17th Lancers
18th May 1915, Temporary Major 8th Reserve Regiment of Cavalry, Deputy Assistant Quartermaster General
25th July 1916, relinquishes rank of Temporary Major.
4th July 1919, ceases to be employed with the Labour Corps (his Medal Index Card shows Labour Corps and makes no mention of 16th Lancers or 8th Reserve Regiment of Cavalry ie he served in a theatre of war with the Labour Corps. He entered France in the last days of the war - 17th October 1918).
12th September 1919, placed on the Retired list as a result of ill health
A summary of his life can be found
online in a Grace's Guide relating to his work with motor cars.
26th January 1947. Died.
So far, I've found no official documentation or any publication to show that Henry Deasy was the Major Deasy who called Guinness. The idea for the improvised armoured cars originated with Colonel Portal, one of the officers in charge of the troops coming from the Curragh (including 8th Reserve Regiment of Cavalry) to which Deasy was attached in a Quartermaster role.