The jury at Lewis Crown court heard how Lauren Bishop, Michael Clark and Edward Phillips, met up after and celebrated by buying and drinking alcohol on the seafront.
CCTV from the Londis store nearby showed Phillips and Clarke laughing and joking shortly after carrying what the court heard was a brutal, vicious and horrific attack.
More top news
A young Scout from Kent has collapsed and died while attending a jamboree in Finland.
Train services through Gatwick Airport face delays and disruption after a track fire closed half of the lines at the station.
Network Rail has reopened two of the four lines but two will remain closed for the rest of the day.