When Holmes and Watson get to the castle at Hellmouth and pick the lock to break in, the door they are picking seen from the outside is an entirely different door that opens when you see them succeed in the following interior shot.
The morning after the dinosaur attack on the East End, Holmes and Watson are having breakfast. Holmes plays a little game of "jacket on, jacket off": when he's shown from the front, he's only wearing his shirt; from the back, he's wearing his suit 7 out of the 11 shots.
In the opening scenes street lights and window lights are shows, but street lights were turned off and windows had blackout curtains to avoid giving the Germans reference points for guidance.
When Thorpe Holmes is showing his brother the bullet that paralyzed him what is shown is a complete cartridge (the bullet and the shell casing) and not just the bullet; upon firing the bullet leaves the gun, but the casing either stays behind (revolvers), or is ejected to the side (automatics.)
Watson is told to bring hid service revolver for a late night stakeout. He is shown using a Colt revolver not the Beaumont-Adams .450 Adams which was the British service revolver between 1853 and 1880
In the opening scenes Big Ben is shining brightly with German bombs dropping and bombers overhead, but the clock tower's light was turned off during the war because it would have served as a beacon to German bombers.
At the start of the movie, Watson, says it is the second time he has watched London burn; however, it would have been the third as the Germans bombed London during World War One and caused fires then. With the events described in the movie as the first London burning, World War One would be the second, and the fires of 1940 would be the third.
In the very beginning of the movie a Kraken attacks the sailing ship in the middle of the ocean. While the crew runs around the boat, a restaurant sign and streetlights can be clearly seen in the background.
In the beginning during the autopsy, when it shows Holmes and the undertaker standing behind the dead man, revealing the man's stomach, you can clearly see that he is breathing.
In one of the exterior scenes an estate agent's sign is clearly visible in frame for a few seconds.
Thorpe holds up the bullet with had paralyzed him and been lodged in his spine for five years. However, what he holds is a complete shell including the case. The shell case would have remained in the gun and only the lead bullet fired into his body.
Watson reads a newspaper at breakfast. The headline on the newspaper relates an air raid in Italy. Very unlikely in 1882, 21 years before the invention of the aeroplane.
There appears to be double yellow lines and a give way triangle in Victorian London.
The very first shot of the film shows London during World War 2. It includes the Barbican (built on land bombed during the war and fully opened in 1982) and the Millennium Bridge (built between 1998 and 2000).
The clock face on Big Ben is lit with electric lights. When this movie was set, it should have been illuminated by gas lamps.
when the balloon carrying Holmes goes over houses, TV aerials can be seen on top of the roofs.
As Watson is scaling the cliff face, using only a single piece of rope for safety, you can clearly see Gareth David-Lloyd's real safety harness.
While Watson scaling the cliff, the rope seen in his close-ups is clearly a new standard-issue climbing rope, while the end of rope held by the helper is old and tattered.
Holmes says he and Watson will take the train to Newhaven but the cliff face seen shortly after bears no resemblance to the chalk cliffs on the South coast near Newhaven.
In the opening autopsy scene, Holmes states that it is ten o'clock. Yet the clock on the wall reads 8:05.