After the family returned to London, Behnes continued his artistic training, studying at the Royal Academy School of Art from 1813, under the tutorship of Peter Francis Chenu.
In 1819 he won a Society of Arts gold medal for inventing an instrument to assist sculpture work, having by this time begun to practice successfully as a sculptor.
His pupils included noted sculptors George Frederic Watts, Thomas Woolner and Henry Weekes,[3] and naturalist Benjamin Waterhouse Hawkins.
He was found lying unconscious in a gutter, with only three pence in his pocket, on New Years Day 1864 and died on 3 January in Middlesex Hospital.
He produced many busts of children, reliefs and also some notable church monuments and statues, including ones of Dr William Babington in St Paul's Cathedral and Major-General Sir Henry Havelock (believed to be the first statue based on a photograph, two casts were made – one is today situated in Trafalgar Square, London, the other in Mowbray Park, Sunderland) and several of Sir Robert Peel (including ones situated in Leeds, Peel Park in Bradford, and at the Peel Centre in Hendon in north-west London).