A survey of 2,000 adults has revealed which classic children's games have stood the test of time and are still considered the 'best playground games' today. Favourites such as marbles, British Bulldog, conkers and 'What's the Time, Mr Wolf?' all feature in the top 10. Meanwhile, the list also included other well-liked games such as football cards, yo-yos, 'Cat's Cradle' and hopscotch. The research has shown that over half of adults spent time outside playing games every single day when they were at school. The majority believe these social interactions were key when it came to making friends ; nearly three quarters regarded these play sessions with friends as some of their fondest childhood memories. Gillian McMahon, executive director of the international charity Right To Play, said: "Play is a deep-rooted part of childhood in the UK; however, millions of children globally are unable to claim this basic right." Right to Play is an organisation which strives to transform the lives of millions of children every year through play. "Extreme challenges such as conflict, poverty, child labour and early marriage are depriving many vulnerable children of the childhood they deserve," Gillian added. The research was published to coincide with International Day of Play, on June 11. This annual UN-recognised day promotes awareness about the crucial role of play for children and underscores play as a fundamental right. The study indicated that the majority of adults were unaware that play is recognised as a basic right for children under international law. However, 67% believe every child should have a right to play, with physical exercise, making friends, and building social skills such as empathy and cooperation seen as key advantages of playing. Gillian McMahon added: "Many children are denied the chance to just be kids. We are working to change this situation. "Through our global programmes, we are reaching more than 4.7 million vulnerable children each year in some of the most difficult places on earth. "Using the power of play we are helping children to stay in school, resist exploitation, overcome prejudice and heal from the trauma of war and displacement."