My recollection of my history classes is that they never fought each other in Spain, but that Wellington developed methods to counter what Napoleon taught his best generals to do. If I had my pick of any contemporary general to go up against Napoleon, it would be Wellington. And vice versa.
Is it possible the panel was influenced by this video? (NSFW for language)
Washington has a fair claim to be the UK’s greatest military foe. He did more than any other individual to militarily win American independence, keeping an army in the field for eight years. He was usually very careful but also knew when to roll the dice, as he did to deadly effect at Trenton, Princeton and Yorktown. After that last defeat, the North government fell, and George III actually drafted a letter of abdication. It was the first time in human history that a colony successfully won its independence and then set up a lasting form of self-government. It was also, if memory serves, the only large war which the UK lost… ever?
Washington never posed the existential threat to Britain that Napoleon did, though, or as Hitler later would, through such talented generals as Rommel, Guderian, von Manstein, etc.