Why I think at least 7 Audax..
You can read the book here
https://books.google.co.uk/books?id=...0audax&f=false
Pride of Eagles
Page 51
Second Ferry
"Four Audaxes had flown to Rhodesia in March (1939) but two were still with the RAF in Heliopolis"
This flight was scheduled to bring three aircraft: two from Cairo, and the Audax that had been left at Malakal on the previous trip"
However, only two reached Salisbury because Graham Smith's machine had to be left in Lusaka
Thus Total = 7 Audax
Frist Trip (5 left 4 Arrived 1 in Malakal) = 4 in Rhodesia
Second Trip (2 left Cairo, plus 1 from Malakal 2 arrived (one from Cario, 1 from Malakal , 1 Left at Luska) = 4 + 2 in Rhodesia plus 1 in Lusaka = 7
I can't read the book any other way
Note: A photo of these last 2 with escorting Rapide SR8 is in the book