Hi Fay,
The hidden London tours are here:
https://www.ltmuseum.co.uk/hidden-londonYou can take photos, but will be handheld only. I'll likely use my phone as it's miles better in low light than my camera but it can save RAW format.
As tempting as it is for photos of Crossrail, I think I'll let Peter show us how it is done!
Ian