V100 Stelvio coolant overflow

My Stelvio has just hit 12000 miles and 11 months’ use. I’ve felt blessed not to have encountered the many V100 engine teething issues, but today I arrived at a weekend event with my club, parked up in the hotel car park only to find pink coolant flowing freely from its overflow.

Anyone have an idea about what is happening here? The coolant has not been topped up (or even checked) since the second service at 7500 and it’s not as though the bike hasn’t been thoroughly ridden in all seasons and temperatures.