Legendary SAS commander Paddy Mayne was denied a posthumous Victoria Cross because of a glaring ‘clerical error’ by two army chiefs, new research reveals.

Lieutenant-Colonel Blair ‘Paddy’ Mayne – whose heroics during the Second World War feature in the BBC drama series SAS Rogue Heroes – was recommended for a VC for smashing through a Nazi ambush in Germany in April 1945.

During the action, he rescued wounded men and eliminated a German machine-gun position.

The recommendation was, however, controversially downgraded in Whitehall. He instead received a Distinguished Service Order – his fourth of the Second World War.

The Mail on Sunday revealed in January that the Ministry of Defence was being urged to reverse the decision.

Now an extraordinary military document discovered in an archive in Canada and shared with the MoS suggest that senior officers assessing Lt Col Mayne’s citation appear to have made an embarrassing mistake by confusing the word ‘signal’ with ‘single’.

The Royal Warrant that instituted the VC in 1856 states that the medal is awarded to those who have performed ‘some signal act of valour or devotion to their country.’

But Lt Col Mayne appears to have missed out because he received help from a comrade who was blasting the Germans with a machine gun which, it was argued, meant his feat was not ‘single’ act of valour.

Lt-Col Mayne, a founding member of the SAS, was recommended for a VC for blasting through a Nazi ambush in Lower Saxony in April 1945

During the action, he rescued wounded men and eliminated a German machine-gun position 

The revelation comes ahead of a debate by MPs in the House of Commons on Tuesday about Lt Col Mayne’s denial of a VC.

A letter written by Brigadier JRC Gannon, a senior British Army officer, in July 1945 praised Lt Col Mayne’s ‘magnificent act of heroism’ but warned there was a ‘certain flaw’ in the citation.

He suggested that he had consulted Sir Colville Wemyss, one of the most senior Generals in Whitehall, who agreed that Mayne’s heroics were not ‘quite up to VC standard’.

Brig Gannon wrote: ‘It was not a single-handed act of heroism, rescuing the wounded, as another officer was present in the jeep giving covering fire.

‘Nevertheless, it was a magnificent performance and it is suggested that the rare distinction of a third bar to the DSO would be the appropriate award.’

Last night historian and SAS expert Damien Lewis, who along with the grandson of one of the founders of the SAS commissioned the research, described the letter as a ‘smoking gun’ that exposes how the officers misunderstood the rules governing the award of VCs.

‘This reveals that the refusal of Paddy Mayne’s VC seems to have been a clerical error or an error of interpreting the rules of how VCs get awarded.

‘Therefore the debate is no longer asking the British Government to overturn decades of military tradition that awards are not revisited retrospectively. It is just asking them to correct an error of fact.

‘It would be very simple to do and it would not set a precedent. It would suitably reward Paddy Mayne and the SAS and also send a wonderful message to Britain’s armed forces today.’ 

Brig Gannon’s letter was found in a Canadian archive because Lt Col Mayne’s SAS unit was embedded with Canadian forces in Germany in 1945. 

The MoS revealed in February how Labour Defence minister Lord Coaker had rejected calls for Lt Col Mayne to be awarded a VC. 

‘No records remain as to why the decision was made, and it would be impossible to second guess the decisions made by military commanders at the time: to do so would be to cast doubt on their competence and integrity,’ he said. 

Lt-Col Mayne’s heroics in the Second World War are featured in the BBC drama series SAS Rogue Heroes (Jack O’Connell pictured as Mayne)

The decision not to award a posthumous Victoria Cross (pictured) was criticised by former defence secretaries including Sir Ben Wallace and Grant Shapps

‘Furthermore, neither this Government nor any previous one has departed from the rule that British awards are not granted retrospectively.’ 

The Commons debate on Tuesday has been tabled by Jim Shannon, the Democratic Unionist Party MP for Strangford in Northern Ireland. Lt Col Mayne was from Newtonards in Ulster.

Mr Shannon told the MoS: ‘As a wee boy growing up in Ballywalter in the 1960s and the early 1970s, Blair Mayne was my hero. He was a hero for every wee boy and probably most wee girls as well.

‘The momentum is growing for this and the interest is growing. We are hoping that the support from across chamber will enable the minister to take this to the next stage and that at long last the wrong that was done against Blair Mayne 80 years ago can be righted.’

Veterans Minister Alistair Carns, a former Royal Marine who has won the Military Cross and DSO for gallantry on operations, will respond on behalf of the Government during the debate.