Who is favourite to win the ATP World Tour Finals at the O2 Arena?
But how good are they at deciphering cockney rhyming slang?
"It was probably one of the most annoying noises I've ever heard in my entire life", Sock said.
It was the American world No 9, the Paris Masters champion, who started the quickest breaking his Croatian opponent in the opening game of the match but he was broken back immediately.
After those two games, the match zipped along at a rate of knots with barely 35 minutes having passed before Zverev was serving to try to force a tie-break. The opening match in the Pete Sampras Group produced a feast of stylish backhands from both players but it was Dimitrov, the first Bulgarian to qualify for the tournament in its 48-year-old history, who overcome some late jitters to prevail.More news: Jon Stewart says he's 'stunned' by the allegations against Louis CK
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The Spaniard is the only one of the "Big Four" never to have won the ATP Finals and has pulled out a number of times previously before the event, which is played on a fast indoor surface rather than his favoured clay.
Cilic looked set to come out on top when he claimed the first mini-break of the tie-break, but Sock showed incredible athleticism to dart in and guide away a victor after a Cilic shot struck the net cord and he won five points in a row to seal a hard-fought victory.
The Swiss went on a run across the end of the first set and beginning of the second, winning 16 of 19 points as Zverev crumbled under the lights and noise of 17,000 partisan fans.
"It's definitely disappointing in both matches in that third set after being in a good position and putting myself in a good position". But the third seed composed himself to hit back and complete a remarkable turnaround to take it into a decider following a loose forehand from the Swiss on his third set point chance in the 12th game. Zverev roared to Federer's crowd who responded with sheer excitement at what they were witnessing.
And it seemed fitting, given Zverev's performance in the last set, that when match point came at 5-1, a double-fault ended proceedings.