In early 1787, Thomas Clarkson, a fellow graduate of St John's, Cambridge, who had become convinced of the need to end the slave trade after writing a prize-winning essay on the subject while at Cambridge, called upon Wilberforce at Old Palace Yard with a published copy of the work. This was the first time the two men had met; their collaboration would last nearly fifty years. Clarkson began to visit Wilberforce on a weekly basis, bringing first-hand evidence he had obtained about the slave trade.