Principal Photography in September 2017

Tintagel, Watford and London appear to be the locations set to start shooting next month. 

The mention of London in this tweet may just refer to studio work with all the exteriors taking place in Cornwall; it may be a catch-all reference to include Watford locations or Warners at Leavesden.

Joe Cornish to direct THE KID WHO WOULD BE KING, a family fantasy adventure which is #filming in London in September. Join the cast! pic.twitter.com/A1LwwPlCoF

— UK Casting News (@UKCastingNews) August 24, 2017

Attack the Block director Joe Cornish to shoot new #film The Kid Who Would Be King in #Cornwall #filmnews #newfilm https://t.co/TJ7IBNOrE0 pic.twitter.com/UgXOThXpe8

— Cornwall LIVE (@CornwallLive) August 24, 2017

Here are details of another 16+ casting call which implies the engagements will begin on 1st September.