Many employers protect their business against unfair competition from former employees by including restrictive covenants within an employment contract.
As restrictive covenants infringe the general public policy in favour of freedom of employment, these can be difficult to enforce unless they are judged to be “reasonable”. The assessment of “reasonableness” takes into account a range of factors, including any employee’s status, responsibilities and overall circumstances.
In PAT Systems v Neilly  EWHC 2609 (QB), the High Court has reaffirmed that the “reasonableness” of a covenant is assessed at the time it was entered into.
If a restrictive covenant is unreasonable at that point, it will remain so even if an employee’s job or circumstances subsequently change such that, had the covenant been entered into at that later date, it may have been reasonable.
The lesson from this case is simple. You should consider refreshing the restrictive covenants (and an employee’s contract) when promoting or substantially changing the role or circumstances of an employee if you wish to be able to enforce these.