14. When the National Assembly recovers the whole or part of any payment made to a claimant, it may also recover interest thereon at the rate of one per cent above the sterling three months London interbank offered rate and that interest being calculated on a day to day basis for the period from payment to the claimant to recovery from the claimant, unless the sum recovered was paid to the claimant as a result of an error on the part of the National Assembly its servants or its agents.