When Giles is shown from behind talking to Lady Megan, his hair is black rather than blonde.
When Giles is shown from behind stopping in the woods near Sir Gideon, his hair is brown rather than blonde.
When the rocks fall down the mining system, it is broad daylight though the previous shot of the fight and the next of Giles and his fencing opponent ending up near its top are at night.
When Giles puts his hand to his chest talking to Valiant in the common room, it turns green like his tunic.