Matchpoint pairs, England.
North's 2NT overcall was alerted, prompting East to ask the meaning. South replied "Both minors".
When North bid 3NT, East asked about 3NT. South shrugged and advised East to check the N/S convention card. In the "defence to weak twos" section of the N/S convention card, it clearly stated "2NT = both minors".
East led ♠A and continued the suit. Declarer won the K, cashed ♦K and played another diamond to the ace. He then cashed his winners in the red suits (with the aid of the marked heart finesse) and so the table result was 3NT+1, N/S +430.
West calls the TD, claiming that North's bidding may have been affected by unauthorised information. If 2NT is natural, then presumably 3♦ should be interpreted as a transfer, he suggests.
The TD asks North why he bid 2NT. He says that he knew that 2NT showed both minors, but because he had thought for a while over 2♠, he decided he ought to bid something and that a slow pass would put his partner in an awkward position.
How should the TD rule?