The RAMC motto; ‘In Arduis Fidelis’ [Faithful in adversity]
Basically John Watson’s raison d’ être. John made his vow to Sherlock the moment he pulled the trigger to shoot Jeff Hope, John’s a man of action not words. We never see him break that vow, question it, yes. But he never takes long to reconfirm his fidelity.
We witness John renew that vow, His Last Vow, in the sanctity of 221B; ‘Your way, always your way.’