As an Ambassador Spire Elite member for 25 years I’ve never used price promise but, booked 2 nights at East Midlands express and found slightly lower price on booking.com. Sent claim form into Ihg but, owing to rate change before they found time to have a look at booking.com site they would not honour the Ihg terms and conditions. They say it only applies when they look at third party site but, if it’s 12 hours later as, in this case then, they will say, sorry rate is now higher on booking.com . Although I supplied evidence and Atlas who own the express agree with me, Ihg will not honour there terms and conditions of awarding membership extra points for the price being lower on a third party site.
So, beware.