During the 1840s he and John Dudney became the centre of a widening circle of friends interested in history – recent, mediaeval and ancient but especially of Sussex – which formed the nucleus around which the Sussex Archaeological Society was formed in 1846. Its first meeting took place in the open air at Pevensey Castle, where Mark Antony read the inaugural address, a paper on the Castle’s history. From that beginning, the Society went from strength to strength. Its periodic publication, The Sussex Archaeological Collections, to which Mark Antony contributed a formidable list of items, gained nationwide and even international respect as a historical journal , and at its headquarters in Barbican House alongside Lewes Castle, the Society established a library rich in Sussex source materials and a museum that today draws thousands of visitors yearly.

It is best known now by the general public for the historical monuments it has lovingly preserved and, if it could boast of no other achievement other than the magnificent preservation of the Roman Palace at Fishbourne on the edge of Chichester, it would still deserve universal praise.When, to the Palace, are added such historical treasures as Lewes Castle itself, Michelham Priory, Anne of Cleves House in Southover and the ancient Marlipins in Shoreham-by-Sea, the esteem in which the Society is held can be readily understood. The portraits of Mark Antony and John Dudeney hanging in Barbican House can look down with pride on the mature development of the Society they brought into being.

For his services to history, Mark Antony was elected a Fellow of the Society of Antiquaries and received an honorary Master of Arts degree from an American university; but although such public honours went justly to him, credit must be given, too, to the father who laid the foundations of his education so soundly and smoothly that Mark Antony did not even realise at the time that he was acquiring them.

Before and during the early years of the Sussex Archaeological Society, Mercy was bearing children. She gave birth to nine, of whom one died in infancy and was buried in Chiddingly churchyard. Meanwhile Mark Antony taught at school, wrote copiously and worked for the Society. In 1853 he closed the Lancaster Street establishment and opened a boarding school at St. Anne’s House in Lewes High Street, where his pupils usually included a number of young Frenchmen. Mercy was the school’s matron.

In 1860-1 Mark Antony was one of the Lewes Headboroughs, but from that point began a decline in his fortunes, partly because of ill-health in both himself and Mercy and partly because the school suffered from the competition that developed with the opening of numerous new public schools for the sons of middle-class parents. On May 31^st, 1867 , Mercy died. Shortly afterwards Mark Antony closed the St. Anne’s House school and moved to Seaford, taking the French pupils with him but precious few others, with the result that his financial position became so desperate that his friends in the Sussex Archaeological Society found it necessary to raise a subscription on his behalf. It yielded £400.