Hi Teej,
In his own book, Snow says Punta Arenas, and that's what he told me a couple of weeks ago when I spoke to him on the phone.
He also saw the RAF roundels and fin flashes.
He knew what a Canberra looked like, and knew they had different noses - either like the Rhodesian ones, or like the South African aircraft. And his cameraman would NEVER have mistaken an A-37 for a Canberra PR9.