Two couples are attempting to seal a new world record for the longest kiss.
Couples warm up for a kissing marathon
James Belshaw, 26, and his girlfriend Sophia Severin, 23, from London, are trying to break the best of 30 hours, 59 minutes and 27 seconds.
The partners are not allowed to sit, or fall asleep, can only take sustenance through a straw and must stay kissing even while going to the toilet.
The record was set in the US in 2001. The new challenge is taking place at the Plaza shopping centre in London.
The pair first locked lips at 1115BST on Wednesday.
To beat the record, the couple, who have been together for three years, must continue kissing until 1815BST on Thursday.
Originally 15 couples applied to take part, but all but one dropped out when they learnt the strict rules under which they would be competing.
A spokeswoman for the shopping centre, which organised the record attempt, said she was confident that the pair would set a new record.
She said: "They are both supporting each other really well and checking the other is OK.
"They are a really strong couple."
He said while the event will be fun and a great spectacle, health and safety checks had to be carried out and participants needed health checks.