About 400 police recruits are to attempt to set a record for the number of people handcuffed together.
Participants will pay £3 for the privilege and the proceeds will go to the Richard House Children's Hospice charity, in Beckton, east London.
Children from the hospice will take part in the bid to secure a place in the Alternative Book of World Records.
The event, expected to last 30 minutes, is taking place at the Hendon police training centre in north London.
A team of officers will be on hand to release the "detainees" once the record has been achieved.
The attempt was the brainchild of recruit trainer Pc Dave O'Grady.
He said: "Each intake of recruits has a designated charity which they raise money for.
"It's not uncommon for the recruits to raise thousands of pounds for their chosen charity."