He is best known for dramatically interrupting the official opening of the Sydney Harbour Bridge in 1932, attempting to slash the ribbon with a military sword while on horseback.

He left school at a young age and joined the Merchant Navy, later serving an apprenticeship with his uncle, an antiques dealer.

In 1920, de Groot returned to Australia and established his own furniture-making business in Sydney, producing replicas of 18th-century furniture styles in Australian timber.

De Groot was a fascist and joined the paramilitary New Guard in 1931, taking part in clashes with left-wing groups.

His disruption of the opening of the Sydney Harbour Bridge was designed to embarrass state premier Jack Lang, a particular target of the New Guard.

Photographs and films of De Groot's actions were widely published and made him a significant public figure, although he played little further role in the New Guard.

He continued his work as a furniture manufacturer and during World War II served with the Australian military, eventually retiring back to Ireland.

He joined the Merchant Navy at the age of thirteen, but later took up an apprenticeship with his uncle Michael Butler, an antiques dealer, for whom he worked for five years in Dublin and London.

He remained involved with the military, joining the South of Ireland Imperial Yeomanry in 1907 and serving for six months with the 5th Dragoon Guards in 1909.

[2] Specialising in Queensland maple, his business proved immensely successful and by 1927 he was reportedly employing 200 artisans at his workshop in Rushcutters.

[2] During the 1930s, de Groot joined a fascist paramilitary organisation called the New Guard, which was politically opposed to the more left-wing government and the socialist views of NSW Premier Jack Lang.

[7] While many accounts say de Groot succeeded in slashing the ribbon, at least one eyewitness has disputed the claim and suggested it was probably broken by the hooves of his rearing horse.

The Mayor of North Sydney, Hubert Primrose, an official participant at the opening ceremony, was also a member of the New Guard, but whether he was involved in planning de Groot's act is unknown.

Detective Superintendent Mackay gave evidence to the effect that de Groot's actions on the Bridge were those of an insane man.

[14] While the first and third charges laid against him were dismissed, the Magistrate did find de Groot guilty of offensive behaviour in Bradfield Highway – a public place.

However, the Museum was outbid by Paul Cave, the founder and chairman of BridgeClimb Sydney, the tourism company that conducts climbs across the Harbour Bridge.