The Concessionaires shall compensate the Harbour Board for any damage to any work forming part of the Harbour Board’s undertaking or to Dover Harbour or its approaches caused by or arising in consequence of the construction or maintenance of any of the specified works or of the failure or want of repair thereof or in consequence of any act or omission of the Concessionaires, their contractors, agents, workmen or servants whilst engaged upon a specified work and shall indemnify the Harbour Board from all claims, demands or expenses which may be made on or against them or which they may have to pay by reason or in consequence of any such damage: