How does JCT clause 3.14 work?

It works in three parts. First, the power. The Architect/Contract Administrator may issue instructions requiring a Variation as defined in clause 5.1, and the Contractor carries them out. The Architect/Contract Administrator may also sanction in writing a Variation the Contractor made without an instruction. That is the route for putting right a change that happened on site first. Second, the right to object. The Contractor may make a reasonable objection, in writing, to a Variation of the kind referred to in clause 5.1.2. That is the second part of the definition of a Variation. It covers obligations or restrictions being imposed, added, changed or removed. They concern access to or use of the site, working space, working hours or the order of the work. There is no matching right to object to an addition, an omission or a change in the quality or quantity of the work itself. Third, no Variation instructed or sanctioned under the clause invalidates the contract. So the Contractor cannot treat a large or awkward change as ending the contract and price the work afresh outside it. The instruction is valued under section 5. Its effect on regular progress goes through clause 4.20 as a Relevant Matter, the loss and expense route. Time goes through the separate extension of time clauses. Four things go wrong in practice. An oral instruction is acted on and never confirmed. An objection is raised weeks after the work started, when it should have come before the instruction was carried out. The objection targets the scope of the work rather than a restriction. And the Contractor claims the amount of change has altered the bargain, when clause 3.14 says it has not.