An employer cannot rely on 'implied consent' when it seeks to change one or two terms in an employee’s contract if those terms do not have immediate effect. An example would be a change to the sickness or redundancy policy. The employer cannot argue that by working without objection for a period of time, the employee has accepted the new terms. If the employee refuses to sign the new contract but simply keeps their head down, tribunals will not blame them for avoiding a confrontation with the employer.
However, where there is a completely new contract, the case of Wess v Science Museum Group (UK EAT/0120/14/DM) has held that an employee will be deemed to accept the changes if they work for a period of time without protest. Of particular importance in this case was that the term had immediate effect on the employee; she was in a new job role. In addition, the EAT noted she was an intelligent and well educated worker holding the position of trade union representative.
Interestingly, the change the employee really objected to, the halving of her notice period, was one that the EAT held does have an immediate impact on employees. It reduces job security and is something staff would have been very aware of.