Factual error: When Bruno is on his way to Union Station, he's heading on a bridge away from the Lincoln Memorial, which means he's leaving Washington D.C. for Arlington, Virginia, or in other words, he's going the wrong way.
Continuity mistake: Early on in the film Alec Guinness is travelling in the back of a van transporting gold bars to the bank. He spots what he believes is a suspicious car following and asks the driver to stop to check it out. The next shot shows the van stopping outside a row of buildings in a London street. The driver gets out to let Alec Guinness out of the van and they are now parked by a low wall with an open vista (probably one of the many bomb sites in London at the time) and no buildings.The next shot then shows the van outside the buildings again.