Insurance is probably a grey area. For example AMEX Plat covers up to £300 for
- £300 for missed departure due to accident or breakdown, travel delay, overbooking, or missed connection
- You will not be covered in respect of the following:
1) Under missed departure and missed connection, claims where insufficient time has been allowed to arrive at the departure point or to arrive to connect with Your ongoing journey by flight, train or ship.
'sufficient time' has not been explicitly defined within the T&C's, nor does it say that all arrangements should be on a single ticket. I would argue that by including ship/rail/air that they imply separate arrangements are acceptable. In the case of onward flights, it is probably reasonable to assume that anything less than MCT would be considered insufficient time.