On the BBC Dirk Marinus and I did some research about a leak from the Dutch government in exile in Britain via the person of Prince Bernhard about the landing of Arnhem.
Did now a bit a new round of research to see how the question now is settled
http://www.independent.co.uk/news/obituaries/prince-bernhard-of-the-netherlands-674988.html

Bernhard's chance to prove himself came in September 1944, when Wilhemina appointed him Commander-in-Chief of the Dutch Forces. The appointment was a ruse by Wilhemina, who feared that captured Dutch resisters would be shot by the retreating Germans as guerrillas. By incorporating them into the Allied forces under General Dwight Eisenhower, she hoped they would be treated as regular soldiers according to the rules of war. A few days later he set up his first headquarters at Diest, just across the border from Belgium. Almost immediately Bernhard became embroiled in controversy.
General Bernard Montgomery was planning an attack to establish a bridgehead across the Rhine at Arnhem. Bernhard later claimed that he and his Chief of Staff tried in vain to persuade Montgomery that the plan was too ambitious. However, after the defeat at Arnhem, it was alleged that there had been an intelligence leak from Bernhard's headquarters, via a Nazi double agent on Bernhard's staff called Christian Lindemans, who was arrested in November 1944. Bernhard protested that Lindemans only arrived at his headquarters three days after the landing at Arnhem. The affair rumbled on until 1986, when the Dutch government released its files on the case. These documents supported Bernhard's contention that he had been used as a scapegoat by the British for the Arnhem débâcle.
And:
http://spitfirelist.com/news/getting-in-dutch-the-third-reich-and-the-royal-family-of-the-netherlands-a-prince-too-far/


Of particular interest to us is the story of the betrayal of Operation Market Garden, which resulted in the Battle of Arnhem, popularized in a major motion picture (based on a book by Cornelius Ryan) “A Bridge Too Far.” 
British Field Marshal Bernard Montgomery envisioned the operation as a way to quickly bring the war to a conclusion. By dropping large numbers of airborne forces behind German lines to seize key bridges and facilitating the Allied advance, the plan was seen as a way to avoid a great number of casualties.
In the event, the operation was a disaster, with German forces slaughtering the paratroopers, many of them before they even landed. Postwar analysis has featured the probable betrayal of the battle plan to the Germans, often pinned on a Dutch resistance fighter named Christian Lindemans, code-named “King Kong.” 
In a book titled Betrayal at Arnhem, author Anne Laurens set forth information suggesting that King Kong was really “Lee Harvey Lindemans.” A celebrated resistance fighter, Lindemans was ordered to pose as a double agent, ostensibly betraying the resistance to the Germans, while retaining allegiance to the resistance as a “triple agent.”
Lindemans was then “left out in the cold” by his control structure, betrayed and labeled as a turncoat to the Gestapo and blamed for betraying the plans for Operation Market Garden to the enemy. He died in a psychiatric ward after the war.
Author Laurens points out that the German units that slaughtered the Allied forces were moving into position before Lindemans was ordered to ostensibly “go over to the enemy” and that he could not have been the agent of betrayal.
The actual “Traitor of Arnhem” had to have been someone else–in these quarters we feel that Bernhard is the most probable candidate.

But when you look at the "about us"
http://spitfirelist.com/about/

Some questionmarks?

Kind regards, Paul.

Paul,

  I'm working my way through the links and yes there is quite a bit of information which over the years have come to light.

Most of the people involved in all the allegations , and those connected with the operation are dead thus we will never know what exactly happened but it is generally accepted that Prince Bernard was a bit of a dark horse and American and British intelligence services did NOT trust him.

But being a royal he got away with it all.

Yet even after the war and in private live he was involved in situations which was frowned upon by many.

I thought Ryan was now totally discredited? From people who have gamed this operation, the general agreement is that it was less "a bridge too far" more "too far from the bridge" - and a few hours later, the panzers would have been well on the way by train, and would have been unable to intervene until too late.