Which preposition to use with justiciars

at Occurrences 2%

Twice a year the officers of the royal household, the Chancellor, Treasurer, two Chamberlains, Constable, and Marshal, with a few barons chosen from their knowledge of the law, sat with the Justiciar at their head, as "Barons of the Exchequer" in the palace at Westminster, round the table covered with its "chequered" cloth from which they took their name.

of Occurrences 1%

LONGCHAMP, WILLIAM DE, a low-born Norman favourite of Richard I., made by him bishop of Ely; became Justiciar of England 1190, and Papal Legate 1191; clever, energetic, just, and faithful, he yet incurred dislike by his ambition and arrogance, and was banished to Normandy; his energy in gathering the money for Richard's ransom restored him to favour, and he became Chancellor; d. 1197.

Which preposition to use with  justiciars