The error is whoever's writes headlines to Sky News. The body of the article has it right:
...nearly 70 years after King Petar Karadjordjevic was proclaimed a traitor by communists....
After Nazi Germany invaded Yugoslavia in April 1941, Petar fled the country and spent the most of World War Two in exile in Britain. After the war, Petar was proclaimed a traitor by the communist leadership, which also abolished the monarchy.
His property was confiscated and he remained exiled until his death in 1970, aged 47, in the United States.
He was buried at a Serbian Orthodox Church monastery in Libertyville, Illinois - the only European monarch laid to rest on US soil.
2013 - nearly 70 = nearly 1943. 1944, probably, when Tito got on top.
He went to the United Kingdom in June 1941, where he joined numerous other governments in exile from Nazi-occupied Europe.[3] The King completed his education at Cambridge University and joined the Royal Air Force.When the Yugoslav Army collapsed, two rival resistance groups formed to fight the occupying forces. The first were the Partisans, a Communist-led left-wing movement encompassing republican elements in Yugoslav politics, led by Josip Broz Tito. The other were the "Yugoslav Army in the Fatherland", commonly known as Chetniks, a predominantly Serbian movement led by royalist General Draža Mihailović, who was proclaimed the Minister of Defence by the government-in-exile. Starting in November 1941, Mihailović attacked the Partisan strongholds, the liberated territories. A Chetnik splinter group, under the leadership of Kosta Pećanac soon ceased operations against the occupation altogether, and focused on defeating the Partisans. In this they found a common cause with the enemy and occasional and opportunistic collaboration between them and the Axis troops began, aiming to stamp out the Partisans.[4][5]
There was no shift of allegiance from Ultra intercepts to be learned in any which way,[citation needed] however, the Allies, with Churchill's insistence, decided to switch their support to the Partisans by November 1943, as their sources came to indicate that by supporting Joseph Stalin and the Comintern the war could end earlier than expected.[citation needed] Through this support of Stalin, Poland, Czechoslovakia, Hungary, Romania, Bulgaria and Yugoslavia were allowed to pass into the Eastern sphere of communist influence. The Partisans soon gained recognition in Tehran as the Allied Yugoslav forces on the ground. In 1944, the Partisan commander, Marshal Josip Broz Tito, was recognized as the Commander-in-Chief of all Yugoslav forces, and was appointed Prime Minister of a joint government.
Peter II of Yugoslavia (links, footnotes at source).
Since 1941, the Second World War was just a series of tragic blunders by Britain and the US. This is one of them.