John fought in the campaigns against the Welsh, 1277 - 1282, taking the place of his father who was infirm. After the death of his father, he was at the Battle of Falkirk, in 1298.
He died in 1310.
His father, also John Lovell, who died in 1287, appears in the The Camden Roll, D 19, where he bears
Barry wavy or and gules a label azure
The John Lovell who sealed the Baron's Letter appears in the following rolls: The Falkirk Roll, H13, and The Stirling Roll, ST57
In these rolls, he bears
Barry wavy or and gules
Since the father of this John was dead in 1301, it is surprising that the seal has the label.
His son, Thomas, also appears in the Stirling Roll, ST58, where he bears
Barry wavy or and gules overall a bendlet azure
There is another John, who appears in The Camden Roll, D44, where he bears
Barry wavy or and gules overall a bendlet argent
In view of the similarity of the differencing of the arms it is likely that he was a brother to Thomas.