It has been a long time since we have seen a promotional code for the Heathrow Express. However, a new offer has just launched – in association with Mastercard – which will run until 31 January 2016.
You need to register with this site, which is run by Mastercard, and then click through the link on that page.
You can combine this link with the KIDSFREE12 promotional code which gives free child tickets. Two adults and two children (5-15), one way, would cost £36.96 instead of £63 by combining the offers.
(Note that you MUST click through from the Mastercard site every time you use this discount. If you try to bookmark the landing page for Heathrow Express and then return to it later, the discount will not show.)
The discounted prices will show up automatically when you reach the Heathrow Express website. You do NOT need to add anything into the Promotional Code box on the booking page.
Here are the prices available via this link, with the normal prices in brackets:
Single £18.48 (£21), Return £29.92 (£34)
Single £25.52 (£29), Return £45.76 (£52)
Still not a bargain, of course, but certainly cheaper than it was!
For details of discounted Heathrow Express tickets for families and group of 2 or more, take a look at this old article.