Such consent not to be unreasonably withheld
When can one withhold one’s consent? When your watchword is “noli mentula esse”.
That's when. As was illustrated in the recent case of Crowther v Arbuthnot Latham & Co Ltd.
If the purpose of a covenant is for a party to achieve a certain purpose, or prevent a certain outcome, then if you use the covenant to achieve some other purpose, you’re likely to get yourself in trouble.