When Sylvester Le Fley (Bob Monkhouse) is informed of the missing artwork by Eric the Watchman (Peter Copley), he runs across the lawn barefoot to the house. When first seen running through the house he's wearing canvas shoes which then disappear as he enters the crime scene and he is once again barefoot.
Le Fley demonstrates the red basket lift of his son's treehouse. The lift is clearly up, when Le Fley receives a mobile call. Next shot the lift is down.
The sandwich does not contain Spam. It's corned beef.