Personally I think the trench coat is the answer as outerwear. It keeps the rain and the wind out, and when it is sunny you can unbutton it and it doesn't sloppy. Guess what - I haven't got one! This year I bought a longed for item a pea jacket so I think next year it is the trench coat. When I buy these items I go large and buy it for ever, so that usually means designer.
And who better or rather more fitting than Burberry for a trench coat. Now I've documented my reasons for staying away from Burberry before so I won't bore you with one of my rants. However I would struggle not to buy a trench from them as the last forever piece in my wardrobe.
I'm always drawn to the black ones more than a camel/ light beige.
Burberry Shower-proof gabardine trench coat £595 Net-A-Porter