This is a fleg.
King George IV passing by the Rotunda Hospital, Dublin – and a specially erected ‘triumphal arch’ – in 1821. in a painting by William Tuner de Londe.
It was the first visit to Ireland by an English monarch since the 14th century.
Older readers may recall our post on the temporary arch for Queen Victoria’s visit to Dublin in 1900.
Thanks Sibling of Daedalus