One of John's principal challenges was acquiring the large sums of money needed for his proposed campaigns to reclaim Normandy. The Angevin kings had three main sources of income available to them, namely revenue from their personal lands, or demesne; money raised through their rights as a feudal lord; and revenue from taxation. Revenue from the royal demesne was inflexible and had been diminishing slowly since the Norman conquest. Matters were not helped by Richard's sale of many royal properties in 1189, and taxation played a much smaller role in royal income than in later centuries. English kings had widespread feudal rights which could be used to generate income, including the scutage system, in which feudal military service was avoided by a cash payment to the king. He derived income from fines, court fees and the sale of charters and other privileges. John intensified his efforts to maximise all possible sources of income, to the extent that he has been described as "avaricious, miserly, extortionate and moneyminded". John also used revenue generation as a way of exerting political control over the barons: debts owed to the crown by the king's favoured supporters might be forgiven; collection of those owed by enemies was more stringently enforced.

What was one of John's principal challenges?