BEGINNING OF HIS CAREER/SERVICE UNDER HIS
UNCLE KING EDWARD I
In the beginning there seemed to be no trouble in paradise.
Grandson of King Henry III, nephew of King Edward I, who
probably arranged for him the splendid marriage with Alice de
Lacy , daughter of Henry de Lacy, 3rd Earl of Lincoln 
[by the death of his father in law, Henry de Lacy, Thomas was to inherit the
Earldoms of Lincoln and Salisbury, added to the Earldoms
he inherited from his father, Edmund Crouchback  namely Lancaster, Leicester and Derby, which made him one of the richest
nobles in the land] ,
what stood in the way of a splendid career?
And it all seemed going just fine:
On reaching On reaching full age he became hereditary Sheriff of Lancashire, but spent most of the next ten years fighting for Edward I in Scotland, leaving the shrievalty in the care of deputies.
He served his uncle King Edward I, by participating in the battle
of Falkirk in 1298. 
NOTES 1 – 250