All Customer orders must be placed in writing. No Contract shall be created unless the Company accepts the order. The Company shall be relieved of its contractual obligations in the event that performance thereof is prevented or delayed directly or indirectly by an act of God, war, riot, strike, labour disturbance, industrial dispute, fire, flood, explosion, shortage of material or labour or any cause beyond the control of the Company. If for any of these reasons the Contract is not completed the Customer shall pay the Contract price less the costs not expended to date. Performance of the Contract is subject to the availability of the Company's property. The Company at its sole discretion reserves the right to substitute unavailable Company property of a similar quality, specification and performance. The Company may sub-contract all or any part of the services. The Company contracts for itself and as agent of and trustee for its employees and sub-contractors and their employees and any reference in these Conditions to the Company shall be deemed to include every such employee and sub-contractor.