Perry Fenwick will carry the Olympic torch as Billy Mitchell in an eight-minute live sequence to be slotted into tonight's (July 23) episode of the BBC soap.
11 regular child actors and 450 extras will appear during the live scenes to cheer Billy Mitchell on during the relay in Walford.
19 cameras will be used around Albert Square to film the live sequence.
The live scenes will also feature Billy's granddaughter Lola Pearce (Danielle Harold) give birth.
Rehearsals for the live episode began on Saturday (July 21), while full dress rehearsals were held on Sunday (July 22).
Perry Fenwick said: "Summer arrives just in time for me to complete my 24th circuit of Albert Square and I'm sweltering! On the plus side, I'm starting to see abs, have buns of steel and the show is looking good too!"
Danielle Harold added: "I have known about this live episode for such a long time but all of a sudden it has crept up on us. I am really nervous but now we have started rehearsing, I am feeling equally excited. It will definitely be an experience and I hope Perry runs smoothly!"
Director Clive Arnold stated: "As the only drama asked to be involved with the Olympic Torch Relay, it is a huge honour for EastEnders and for everyone involved - a truly once in a lifetime opportunity.
"I was so excited and thrilled when I was asked to be part of the episode and I know that every member of cast and crew feel exactly the same way."
Fenwick recently told Digital Spy that he was feeling "nervous" about the live episode.