File:Coat of arms of the King of Ireland, Feuillet 6 de l'Armorial Le Breton.png

"Le Roy d'Irlande" Coat of arms of the "King of Ireland", Feuillet 6 de l'Armorial Le Breton. Possibly the heraldic badge of Robert de Vere, Duke of Ireland, Marquess of Dublin, 9th Earl of Oxford (1362-1392). Royal crest of Ireland: (On a wreath or and azure): A tower triple-towered or from the port a hart springing argent attired and unguled of the first (Source: Fox-Davies, A.C., 1915, The Book of Public Arms, London). Possibly originally the heraldic badge of Robert de Vere, Duke of Ireland, Marquess of Dublin, 9th Earl of Oxford (1362-1392).

The device is shown in various European 15th century armorials on a shield as the coat of arms (not the mere crest) of the so-called "King of Ireland", with varying tinctures. It seems that the person referred to vaguely as "King of Ireland" was Robert de Vere, Duke of Ireland, Marquess of Dublin, 9th Earl of Oxford (1362-1392), a favourite and court companion of King Richard II of England. Indeed it seems to be accepted that the white hart is borrowed from the impresa (personal emblem) of King Richard II which was A hart couchant argent, attired, unguled and shackled or. A magnifique example of this impresa is on the back of the Wilton Diptych, (c. 1394-9), today in the National Gallery in London. The white hart in the crest of Ireland thus points again to Robert de Vere, the favourite of Richard II and would-be (sic) Duke of Ireland. The tower triple towered may be determined in that case to be the Castle of Dublin, the city of which he was created a marquess for life in 1385. A thirteenth century seal matrix of the city of Dublin that features a triple towered fortified structure being defended under siege, is not contrary to this opinion. (Hubert de Vries on his website De Rode Leeuw (http://www.hubert-herald.nl/), quoted in J. Paul Murdock, "Royal Crests - Ireland, 19/12/20190" (blog) [1])

Ireland was considered a mere lordship (rather than a separate kingdom) of the King of England until King Henry VIII had himself proclaimed King of Ireland in a personal union with the Crown of England, thus separate arms may not have been used. When King James VI of Scotland became King James I of England and thereby created Great Britain, the Irish Harp appeared quartered in the British royal arms. The Buck and Tower device appears thenceforth to have served as one of the three crests of the new Stuart monarch: At the funeral of King James VI and I was likewise carried the standard of the crest of Ireland, a buck proper (argent in the draught) issuing from a tower triple towered or, which is the only instance of this crest that I have met, and therefore was probably devised and assigned for the crest of Ireland upon occasion of this funeral, but with what propriety I do not understand. (unspecified author, Questions and Answers, Notes and Queries (a 'Medium of Inter-Communication for Literary Men, Artists, Antiquaries, Geneologists, etc, published by George Bell of Fleet Street, London in 1855) (quoted in J. Paul Murdock [2]). ​The crest with the springing hart was intermittendly used for Ireland until the end of the monarchy and its replacement by the Republic of Ireland. The device is not used by the Republic of Ireland (see w:Coat of arms of Ireland).