Throughout the Vietnam war, the Brits frequently staged through Saigon TSN. The Argosy did not really have the legs to fly Changi-Kai Tak non stop with sufficient to make the diversion to Manila, if the need arose.
When posted to HK from Borneo in Mar 67, I first went to Changi and thence by Argosy to HK via Saigon.
In a very childish gesture (it now seems) I sent picture postcards to a couple of girlfriends in UK to say I was in Vietnam!!!
O-D