bjcc,
At last you believe me. Your concern about an offence under the ANO. Yes, maybe but not for the ATCO who is innocent. This may be an offence by the management by letting the ATCO continue whilst they thought he was under the influence. This to me comes under the "endangering an aircraft and it's occupants" article in the ANO. Everyone is innocent until proven guilty, and as far as I'm aware there is no proof. But the ATCO concerned was allowed to continue working whilst thought to be under the influence by the management. The guilt is therefore on the management and any offence is committed by them.
ils 119.5