Headed to London? Have Gold status with a Star Alliance member airline such as Singapore Airlines, United Airlines, Air Canada, Lufthansa, Swiss or any of the group's 23 other carriers?
Then a flash of your Gold frequent flyer card is all it takes for a free upgrade on the Heathrow Express to the train's Business First class carriage.
The Heathrow Express is the quickest and easiest way to scoot between Heathrow Airport and Paddington Station, where you can settle into your hotel or hop a Tube train or an Uber to your final destination.
And even though it's a zippy non-stop journey, being able to step up from the standard Express carriages to Business First is still a treat.
Located at either end of the Heathrow Express, these swish Business First carriages offer more legroom than the regular 'economy' carriage, wider seats, a personal table and even an AC/USB sockets at each seat in case your device needs a fast top-up. They're also less crowded and therefore quieter than regular carriages.
A standard Express fare costs £25 one-way, or £37 for a return journey, with Business First at £32 one-way or £55 for a return trip.
So what's the trick to getting a free first class bump on the Heathrow Express?
Just buy a Heathrow Express ticket for regular Express class, but make your way to the Business First carriage and settle in.
When the conductor passes through, simply show your ticket and your Star Alliance Gold-grade frequent flyer card – or the digital card on your airline's own smartphone app.
Note that the terms and conditions of this Star Alliance offer specify "you must purchase of a full fare standard class ticket to and/or from London Paddington and Heathrow Airport", which may seem to rule out taking advantage of the heavily-discounted advance fares which can be as little as £5.50 one way when purchased 90 days ahead.
However, many frequent flyers have report no issues with claiming their free Star Alliance Gold upgrade to Heathrow Express Business First against an advance fare.