If a contractor flatly refuses to comply with an instruction, and also will not permit the employer to give access to the site to another contractor, what can be done?

Clause 3.10 of JCT Standard Building Contract 2009 states explicitly that contractors are obliged to comply with instructions from the architect that are contractually supported. Should they fail to do so, architects are entitled to issue a written compliance notice under clause 3.11. From this point, the contractor is given 7 working days to comply with the contentious instruction(s). Should the contractor fail to do so then the employer is legally entitled to instruct someone else to do the work and can deduct suitable costs from the sum implied by the contract.