Princess Anne famously believes that there's no such thing as bad weather, only inappropriate clothing and I couldn't think of a more "appropriate" jacket style for summer than denim. It's incredibly versatile and the Princess Royal just wore a rather fabulous denim blazer for a day at the Commonwealth Games in Scotland.
It's possible she's had this in her collection for decades but it stood out as something quite different for her. Anne's jacket was a mid-blue wash and I firmly believe this is the best colour to go for if you want all-round wearability. Indigo, black and white denim are less mottled and can often be stiffer too.