Hi @MetroTrekker ,

I’ve got a few answers for you. I’m a UK citizen, but have lived in NL for many years, so have been to the UK (and back) on an Interrail pass. In answer to your questions:
 

• Question 1 - Any journey you make inside your country of residence has to be part of the journey (on the same day, I believe) to exit or enter the country. So you could do Southampton or Manchester to London to catch the Eurostar to Lille, but you cannot do Southampton to Manchester airport on a different day. I think the app may also reject a Southampton to Manchester itinerary unless it’s part of the same day’s travel to leave the country, in which case it will ask “would you like to use up your country-exit day on this journey?”
• Question 2 - usually the guard/conductor on the train scans the QR code of the Interrail pass in the app. Sometimes they just look at it to check it’s validated for that day, and sometimes they just glance at it and say “ah, Interrail ticket eh?” The app does reject certain tickets or itineraries.
• Question 3 - in my experience the app usually does not work on UK ticket gates and you have to find someone to let you in/out. That’s usually fine - they have a quick glance at your Interrail app and then let you through. In Spain I was given a platform ticket by the ticket office when I showed my Interrail app - that might also be possible in the UK.
• I think you either need to use the app or the paper ticket, one or the other, but someone else on these forums will have a more certain answer.

Good luck! It’s fun once you’ve started!

BTW don’t forget to book your Eurostar seat reservation well ahead of time - the trains get quite booked up. If there’s no availability London-Lille it’s also worth checking if there is availability from London-Brussels on the same train as they seem to have different seat allocation numbers for different destinations.

Thank you for this. So if I didn’t do the Eurostar the airport run would be valid as it’s exiting the country? Or does it have to be to an outside train station?

@MetroTrekker I don’t think exiting the country by plane counts - it has to be exiting by train. So yes, it has to be to a train station.

The problem is you can use a Interrailpass just on 2days within your Homecountry 

Which means you could only 2 of your 4 Journey´s with a Interrailpass as UK Citizen as all of your 4 trips have Parts in the UK

Ok, thank you. So if I used it just Southampton to Manchester and back that would be fine?

In the conditions of Interrail yes. 
but many British Railcompanies doesnt like that you use a Interrailpass just within UK as UK Citizen. Sometimes they ask to see if you used it outside of the UK. :D 

I know sometimes a 4days pass is cheaper as the regular british offers.    

Interesting. Seems unfair though. For all they know my train abroad could have been cancelled.

You can use Interrail to get to or from an airport or port in your country of residence. There is no obligation to leave your country by rail, to be able to use the inbound/outbound journeys. In practice, you have 2 travel days that you can use freely in your country of residence. The app doesn't reject any journey as long as you stay within those 2 travel days intended for inbound/outbound journeys.

Thanks for clarifying, I did wonder this. If for whatever reason I didn’t take the train abroad, e.g. it was cancelled or the available trains no longer worked with my plans, and I tried to return from the airport to Southampton, with the other only logged journey being to the airport (so both inbound and outbound journeys within UK and nothing else), would the app reject it? @seewulf above mentions that some rail operators get a bit grumpy about this.

That app not-really-it has been said several times to you now: the only thing it registrates is MAX 2 traveldays IN homecountry. That is as such a lot easier/generous as paper passes, where one has to write down the trips IN country (and OUT)

There have indeed been a very few-but I dk from how long ago- notes in british train-forums that some conductors insisted on seeing evidence that one had been out of UK or-going to airports, a flite booking. As indeed the cheapest 4-day pass can well cost less as even an advance booking on what once was BritRail. Being non-Brit, no idea how frequent/prevalent this is or just scaremongering. Have travelled many times in GB with IR-pass and it always surprised me how cursory the looks on it were-in other countries checks tend to be much more stringent. The nasty thing is passing gates: always have to use the manned gates and these seem to multiply every time I get there. IF probs are reported they are nearly always about Lon-Overground and/or now the new Elisabeth line.

Much more likely reason to have to turn back at the mo are strikes or ´industrial actions´ in either on rails or in the air or in -ports etc.

The app itself wont reject it as you stay within your 2days in Country of Residence and as @mcadv  discribe it above. there are few conductors on the British Railnetwork that wanted to see evidence that you have used your pass abroad (e.g. many domestic travelers added a foreign trainride on the same day when they used it domestic. like Paris Lyon + (Flight they never took) + Manchester Airport - Southampton 

It is of no interest whatsoever to UK ticket inspectors how you use the Interrail pass  They are only interested that it is valid and the train you are on is listed in your pass, just like any ticket.  The policing is done by the app, which diligently tracks the 2 days and will not allow any further travel in your home country after it registers a second travel day usage in the home country.

I suspect you are thinking of the days when only paper passes were used and they were checking whether the user was a Brit trying to use it exclusively in the UK, which wasn’t allowed.

Now, with a mobile app, the In/Out rule is very simple in application - For up to 2 travel days of your Interrail Global pass, whatever length or type, you can use your pass in your home country as if you were in any of the countries that the pass covers.

That means you can use it to get to or from airports or ports , leave or return to the country by a cross border train or even do a couple of day trips in the UK and fly In and Out to use up your other days. You can even use it to get to an airport and onward travel in your destination in the same travel day (Trains scheduled to leave the boarding station between 0000 and 2359 CET)

 

Oh, interesting you can use the home-country travel days so liberally - I never knew that and always thought you had to be exiting or entering the country by train. Thanks for the update!

You can't use the app as your ticket just like that if your paper pass doesn't get delivered on time. In that case you need to exchange the paper pass for a mobile pass and you need to check what conditions the National Railways portal has for making such an exchange.