old endowment policy

My partner used to have a flat in early 2000. Prior to gettting rid of the flat he had remortgaged it when his then partner split. When the house was remortgaged he continued to pay the joint endowment.
The remortgage was through northern rock but the endowment was with lloyds tab. Where does he go to investigate this? and see if there is any money to obtain from this.