Artists and photographers are everywhere in the museum. The British Museum is the most user friendly museum in the world! The only time you will be reprimanded by the museum staff is if you touch display objects or act like a obnoxious idiot. I only encountered one idiot at the museum and he was promptly descended upon by several stern but polite staff members. Flash photography is not prohibited and it is common to see artists sitting in the aisles sketching with charcoal and water colors. If you want to use oversize cameras with tripods or movie equipment, you will need prior approval but that seems to be just a formality because, judging by the number of news crews and zealous amateurs, I assume that if you ask for special permission, you will allowed to bring your equipment into the museum without any problems.