Fair skinned, freckled Mycroft is very prone to sunburns. One summer, his neck and shoulders get burned very badly while he's got a day off and it hurts a lot when he has to put the suit back on for work the next day. Good thing DI Lestrade notices and offers to help him put some 'after sun lotion' (is that what it's called in English?)on. Let's have lots of UST and please make it prerelationship. Everything else is totally up to you.