Simplify the following text for a Grade 8 native English-speaking person.
Original: Between 1418 and 1436 he was at the convent of Fiesole where he also executed a number of frescoes for the church , and the Altarpiece , deteriorated but restored . A predella of the Altarpiece remains intact in the National Gallery , London which is a superb example of Fra Angelico 's ability .
Simplified: Between 1418 and 1436 , Fra Angelico painted an altarpiece for the church in Fiesole , which has been damaged .