It is complicated. Obtain the ACAS Code of Practice 2000. A dismissal for lack of capability to carry out the work the employee was employed to do is potentially fair under sec. 98(3)(a) Employment Rights Act 1996. I quote from a textbook: M. Sargeant: Employment law, 2nd ed., Longman 2003, page 151: The employer has a right not to have their business affected by an imcompetent employee, but the employee also has a right to be treated fairly (...). Treating an employee fairly does not necessarily mean not dismissing them because they have many years of services. (...) An unreasonable procedual delay, however,