The show doesn't get Mayne or Stirling quite right apparently, though the actors performances are good and draw the average viewer in, but it does get most other characters right and is pretty faithful to true events.
Payne was a big fella mind. Heavywieght boxer for his University, becoming Irish Universities Champion and lost in the final of the British Universities Championship on points.
Before the intervention of the war, Mayne was selected for the 1938 Lions Tour to South Africa despite only having a handful of Ireland caps to his name. Lasting over three months and including 24 matches, the Tour ended in a series defeat for the Lions as Mayne played in all three of the Tests and featured 20 times in total. That says a lot because those tours were brutal. At the time South Africa were hailed as the unofficial world champions as they had beaten the All Blacks in New Zealand the year before. Despite the Lions losing, the South Africans thought he was one of the greatest forwards they’d ever seen playing, he was hard, he was abrasive and not afraid of taking retribution. After the first Test a South African journalist described Mayne as ‘outstanding in the pack and stood up tirelessly to an unwinnable task'.
There are different accounts of Stirling's first meeting with Mayne, one of which has Mayne in prison for having struck his superior officer. It's probably not true but there are other accounts of him having beef's with officers and his off field antics with the Lions were apparently even more legendary than his performances on it, to the point the Lions skipper reckoned he spent almost every morning intervening and pleading with the Colonel managing the tour not to kick Mayne off it for his night before because he was too vital on the pitch.
So I think the show might not have got all the details right - Stirling never swore for instance - but they have got the spirit right. For instance Dudley Wrangel Clarke (the Dominic West) character did invent a fictitious SAS regiment and he was arrested as a spy in Madrid at one point, dressed as an unconvincing woman.
These SAS men were usually guardsmen who then joined the commandos and then joined the SAS. In short they were adrenaline junkies so tearing through a desert in a jeep while a punk rock song is blaring out seems to capture that to me.
Also, compared to a lot of shows they have actually got a lot of details right. On that first jump Stirling and Lewes really did tie their parachutes to the chair legs. The iconic photo jedi posted is almost indistinguishable from a still from the show.
What I like most is it brings home via drama the both the daring of the missions, but also you can appreciate how the blueprint for much of the SAS was laid down early. The small four or five man units, the premium put on intelligence, questioning, understanding the purpose of a mission and improvisation skills.