 As early as June 1298 Lamberton had won victories for the Scottish cause; his activities led both the King of France Philip IV and Pope Boniface VIII to pressure Edward I to halt his attacks on Scotland.It led to Scotland's deposed king John Balliol being handed over into papal custody in 1299.In a letter to Scottish leaders dated 6 April 1299 Philip IV commended Lamberton's efforts and declared he would assist Scotland.