The interesting thing is that the Rail Delivery Group (of which Heathrow Express is a member) seems to say that Eurail/Interrail are valid on the trains of all of their members (see this post). And that's also what the Interrail and Eurail websites are saying. As far as I know, RDG is the authority in GB for these things.

@Nanja, if Heathrow Express are claiming Interrail/Eurail aren't valid, maybe you should contact them or the RDG?

Quite strange i used them several times with Interrail and had no issues

The question here is does Heathrow Express differ here between Eurail & Interrail?

The Heathrow Express Website says

BritRail Passes

Holders of the following passes can use them on Heathrow Express, providing they have first validated them at a Heathrow Express ticket office or a main-line rail station.

BritRail Pass + Ireland
BritRail Consecutive Low Season
BritRail England Consecutive
BritRail Flexi Guest Pass
BritRail FlexiPass
BritRail Party Flexipass
BritRail Consective Eurail Passholder
Britrail Europe
BritRail Point to Point (must state London-Heathrow and vice versa).

I’m not sure what a BritRail Consective Eurail Passholder is, but the word Eurail is on the website. 

There are in fact 2 different types of train on this line: the EXpress=non stop and quite pricey for normal tickets and the now much cheaper local, makes also a few stops in between and even accepts the Oyster-except I think the last leg into airport (travel between terminals is free for anyone).

I have also used an IR-pass once for the Express-but cannot remember any probs-long ago, or maybe there was not even a check.

it is indeed a bit strange that EU and Brit Rail seem combined here-maybe some heritage from the past when EUrail was not accepted IN GB!

Maybe they just forgot a line break between "Consecutive” and "Eurail”. "Britrail Consecutive” would be the pass that covers all of GB.

Thanks all - Yeah @Nanja  I would be interested to see what Heathrow Express and/or RDG say because the rail attendant said to me “we keep telling Eurail we dont accept these but they don’t seem to listen”.

Also in response to @mcadv  the QR code that gets generated doesnt work to get you through the barriers (same with Eurostar tickets by the way) so the attendant will always have to manually check

The Website MyInterrail.co.uk (Interrail selling platform of National Rail) says:

Your InterRail Pass is valid on trains from all of these companies (ATOC), except the Eurostar and the Heathrow Express.

Thanks for flagging. I will have it checked will get back to you with an answer as soon possible. Have a great weekend ahead! 

Just had the same issue…Global pass….trying to get from Paddington to Heathrow….on the search only brings up Heathrow express journeys, even when we ticked valid with eurail pass only….attendant said no…after much searching figured out how to get on a TFL not express train…so all ok but very confusing and frustrating.

Hi everyone, Sorry for the delay, my colleague is sick and I’m trying to pick things up in the meantime. The Heathrow Express is not included in the pass anymore, we have adjusted the app and the website accordingly. However, you can take the Elisabeth Line (run by TFL Rail) to reach the Heathrow airport. I hope this helps Cheers,

Interestingly, they still mention Eurail on their website.

In addition, the Great Britain page and the page with "rail companies covered by the pass” still refer to a list on the RDG website that includes Heathrow Express. The same on the Eurail website.

So the information is still far from consistent.

This is all very confusing. I want to go from Cardiff to Heathrow in August on a Global Eurail pass. I go to “book reservation” on https://www.eurail.com/en/... and it comes up with itinerary but cannot book reservation. It says to go to acprail.com

Ok. Fine… I go and choose reservations and get

•  Train 850 - Depart Cardiff Central at 08:50 - Arrive London Paddington at 10:59 ( ATOC)
  Information: Great Western Railway
•  Train 1125 - Depart London Paddington at 11:25 - Arrive Heathrow Terminal 5 Rail at 11:47 ( ATOC)
  Information: Heathrow Express

Perfect…. Er. Except when I read the chat above, it seems that HEX is in fact not valid. So I can buy a reservation but they wont let me on the train?? Great. Which scares the heck out of me for the Cardiff leg… Given that ACP is letting me reserve a non-existent ticket, how do I know I will actually be allowed on the train in Cardiff even??

I’d be a lot happier if I could book at least “something” on eurail.com

RES for trains In GB an only be done at counter, for free. And its optional.

To reach LHR-READ above: there is beside Expr also now Elisabeth brand new line which has slower all-stops trains (used to be named HR  connect), ev 10/15 mins and these are included. Gain access to platf by manned gate and show pass (probably have to do same at exit Paddingt)

Hi Mcadv, thanks for the [very!] fast reply. Considering just the Cardiff → Paddington (or Cardiff->Reading) leg, I see ACPRAIL is asking for $10, which I am happy to pay for the peace of mind. Will that reservation be valid with my Global Eurail pass?

or via GWR as explained by @rvdborgt  in the How to get reservation post here.
 

@ReadyToHop  Heathrow Express refuse to accept Interrail / Eurail but you can use the services of TfL on this route former known as “Heathrow Connect”


@Nanja@Marion@Felipe.iturrieta  something that have to be solved in the Railplanner or you get in contact with HeathrowExpres to solve this.
 

Oh wow. That GWR link is perfect.

All booked [I have young kids so want to make sure they are in a different carriage to me].  Oops. Typo. :-)

Hello, would like to confirm if Heathrow is not included in Eurail global pass ? 

Hi yes it is confirmed. You can use the Elisabeth Line instead.

Update: changes have been made to our app and website to show that the Heathrow Express is not covered by the pass. Apologies for the delay. This was due to dependencies on other parties with regards to being able to show it in our timetable with the right attributes. 

The Eurail Pass has been removed from the list that was stated on the Heathrow Express website. As for the RailDeliveryGroup website, this information will remain correct. Heathrow Express is still a member of RDG and FirstGroup, they simply decided not to accept Interrail and Eurail Passes on their services.

The line on which Eurail Global Pass is valid is the ‘Elizabeth Line’, not ‘Elisabeth Line’. 

Has anyone used their Global pass on the Elizabeth line recently? I dont want to get stuck at the last minute on the way to Heathrow airport on the way back to Australia! thanks for any feedback.  I read that Heathrow express wont’ accept the pass anymore.