according to john of nikiu, david and his brother martinus were involved in the banishment of pyrrhus of constantinople to the exarchate of africa. this could be seen as a reaction to pyrrhos bypassing david and martinus after the death of heraclius. however, the two princes were too young at the time to have taken an active role in any banishment and the account by john of nikiu is so contradictory that no safe conclusions can be drawn from it. the main source for the life of tiberius is john of nikiu.