Jack Harkness prided himself on his language skills. He knew the appropriate tone to use when speaking to a member of the Lonarian royal family. He knew the arcane expletives one should use when attempting to break a Prolix to harness. His reaction to seeing the crystalline falls of Denubis 5 had caused the planet's poet laureate to retire on the spot, swearing he could not better the poetry of Captain Harkness should he try for ten thousand years. He was the only non-Uxarian to have mastered their language, even though having less than three throats and six sets of vocal chords was generally deemed to be an insurmountable barrier. He had used his language skills across the seven galaxies to flatter and cajole, to persuade and seduce. All in all, Jack often told himself with a self-satisfied grin, he was quite the cunning linguist. But, as Ianto Jones emerged shyly from his bathroom, naked and beautiful, completely exposed to Jack's hungry gaze for the first time, the only word he could remember from his vast lexicon was...

'wow'