There was a difference to the world. Not that they were in London but that the projections were becoming aware of the intruder. It was an air that Arthur was most certainly familiar with but that didn't mean he was comfortable with it.
He watched Charles as things escalated slightly. "Hypothetically, they should, though there's the theory that anything that might be done to ensure I didn't know you were here could trigger them in another way. Not to mention if the dream could survive making the dreamer forget one part of it."