1. A method of controlling a monitoring function of a processor, said processor being operable in at least two domains, comprising a first domain and a second domain, said first and second domains each comprising at least one mode, said method comprising the steps of: setting at least one control value, said at least one control value relating to a condition and being indicative of whether said monitoring function is allowable in said first domain; and only allowing initiation of said monitoring function in said first domain when said condition is present if its related control value indicates that said monitoring function is allowable.