Did a little digging, Constantine converted, no doubt about it IMHO.
Don't want to trust Wiki at all, but this is pretty much what I have read elsewhere.
'His reputation as the "first Christian Emperor" has been promulgated by historians from Lactantius and Eusebius of Caesarea to the present day, although there has been debate over the veracity of his faith. This debate stems from his continued support for pagan deities and the fact that he was baptized very close to his death.'