I knew it was time to put them on my car when I nearly had it sideways on the roundabout going to work on a cold morning last week.
Couple that with an interesting trip out of an icy Cairngorm car park in an E46 330i a couple of years ago has taught me all I need to be persuaded that winter tyres are a great idea in Scotland, if only to traverse the col du Dunfermline confidently.