I've always admired Helen Mirren as an actress. Now I also admire her wicked travel skills. According to this article Mirren never takes her own clothes with her when she travels. Instead, when she arrives at her destination, she has her driver drop her off at a good charity shop and picks out all the clothes she'll need while she's away. On her way back to the airport, she drops the items at another charity shop.
Perhaps she just got tired of lugging around a big cardboard box?