What he's doing is the 'I know something that my job prohibits me to discuss publicly' approach.
Heard it a million times. It's tiresome, especially when the issues are documented publicly. Hansard contains a lot of interesting detail on the topic, for instance. Try the Channel Tunnel Security Regime debate in the Lords (2014) for instance, where the size of the bomb needed to breach the tunnel (to the sea) is openly discussed.
It's hardly reliable, and the passport connection will need to be a MFA link to the home office system, so a broken connection will likely require reauthentication. Also, all the checks need to be done before the tunnel because theres no internet connection inside. That's 1hr journey time from Brussels to check 800 people.
This is why you need a technological solution. The UK is heading in the right direction, and I think it's reasonable to expect Eurostar to do proper checks on check-in to ensure that Mr. A. Terrorist is the same bloke as on his identity document. With that, you already have all the data locally and you don't need a permanent connection, because each device already contains everything known on the passengers that have checked in.
Doable, but honestly, the onboard checks are much more cumbersome and annoying than the juxtaposed controls. It's also much more convenient to interview people in civilised conditions rather than in the cramped conditions onboard, so I think the juxtaposed controls are better for everyone.
I can give an example: the overnight sleeper train from Wrocław to Lviv. It would be logical to have juxtaposed controls for the departure from Lviv, as it would allow people to sleep and it would remove the lengthy stops at the border. Instead, you get disturbed about 1am for the Ukrainian controls, then it takes until about 2am (Polish time) for the Polish controls to be completed. It means that you don't get to go to bed until 3am or so, which is useless.
It's the same problem in the direction of Lviv, where controls are carried out about 3am Polish time. Juxtaposed controls carried out in Lviv would allow for people to sleep straight through for the 6am arrival, which is far more civilised. As it stands, in summer, you can't really get to sleep until 9-10pm due to the light outside, and then you're woken up at 1-2am for the Polish border control.
The juxtaposed controls are really a genuine success story on the part of the UK and France/Belgium/Netherlands, and I see no reason to bring back onboard checks.
And the UK govt has shown it sometimes prefers theatrics and symbolism over pragmatism on the subject of immigration for domestic political purposes.
Indeed. Let's not forget this: theatrics and symbolism are much more important in politics than substance.