Anthony entered into a contract with Bruce to refurbish a block of 100 flats; the work was to be completed in three months. The contract stated that late completion would be charged at £5,000 per day. Anthony sub-contracted with Clive to install the fitted kitchens and bathrooms in each of the flats for a fixed price of £100,000. After a month it became obvious to both Anthony and Clive that Clive had grossly underpriced the cost of the materials and he would be in financial difficulties if he completed the job. Consequently, Anthony offered to pay Clive an additional £300 per flat provided they were finished before the completion date. Clive carried on with the contract and completed the work in time. Anthony is now refusing to pay him the additional money. Advise Clive.