He served as Bishop of Winchester from 1346 until his death, Keeper of the wardrobe from 1341 to 1344, treasurer from 1344 to 1356, and finally as chancellor from 1356 until he retired from royal administration in 1363.

Edington's reforms of the administration – in particular of royal finances – had wide-ranging consequences and contributed to the English military efficiency in the early stages of the Hundred Years' War.

The position was an important one; the wardrobe functioned as the treasury while the King was on campaign, and Edward strongly resisted any attempts to limit this royal prerogative.

The King must have been impressed by Edington's performance, because in 1344 he made him treasurer of the realm, a position he held for the exceptionally long period of twelve years.

This did not entail controlling the King's use of his resources – a move Edward would have resented greatly – but simply attempting to budget all revenues and expenses.

Also, the King was eager to reward his capable servant; in 1341 he was given the prebend of Leighton Manor (Lincoln), by 1344 he also held that of Netheravon (Salisbury), and by 1345 that of Putston (Hereford).

He was not entirely detached from his episcopal duties, however: he used the see as a source for extensive nepotism, yet he also initiated wide-ranging building works on the nave of the cathedral.