Even from the new HS2 platforms? Are you sure about that?
From the nearest HS2 platform, via the new eastern entrance of Euston, along Phoenix Road and Brill Place to the Midland Road door of St Pancras is less than half a mile, yes.
Bully for you, so can I but not when I have my wife with me, and neither can a great many others. As I've said before, it's easy when you know the way, but not all travellers do, many have suitcases, and many would be simply unable to walk this in 8 minutes even if they knew the way. This thread is not targeted at you or others like you, unless you wish to help.
Well I do wish to help, and perhaps unlike most commenting on this thread, I have actually looked into the problem in a professional capacity.
A very significant majority of people travelling specifically between Euston station and St Pancras (or Kings Cross) station are more than capable of walking, and they do. I see them every time when I do the walk which is several times a week. Very, very few have heavy luggage, and even then many walk. Realistically, we are talking a handful of people a hour that would need the assistance of some form of powered transport between the two. Today most that need the assistance due to heavy bags or being less mobile will take a cab, bus, or (if they haven’t done their research) the tube; it’s as much effort to get up / down the three levels to the tube at Euston and the 2/3 at KXSP as it is to walk.
So the need is relatively small, and certainly less than 1% of people doing the trip.
There are only three solutions to providing some sort of moving walkway / people mover / rapid transit. Street level, above street level, or below street level. Let’s take them in turn:
Street Level means either i) closing one or more roads to all vehicular traffic in full or part, elements of which provide the only vehicular access to some properties, or ii) demolishing listed buildings / social housing / places of worship / all of the above. Either option is very difficult to get consent for, and also very expensive.
Above street level also means closing or restricting one or more roads, or demolition, to provide space for the columns necessary to support it. You then run into the issue of a good number of Camden folk having a view of a walkway / transit out of their bedroom window, or alternatively the walkway / transit users having the opposite view. Again very difficult to get consent for, and elevated metro / walkways are not cheap.
Below street level on that side of Euston is already congested with full 5 separate rail tunnels on three levels and three alignments with the levels changing, plus deep basements of the Library and Francis Crick, plus all the normal gubbins of utilities, plus the safeguarded Crossrail 2 zone. At the St Pancras end you have the Thameslink tunnel and station box plus the basements of the Midland hotel in the way. There is nowhere to go at a reasonable depth. You *could* go anywhere you like if you are prepared to go about 40-50 metres deep, but to do that you need to build two very deep access shafts at either end, which would take a couple of years to build and lots of material in /out, and I have no idea where you might locate them that wouldn’t interfere with the existing tunnels or stations. Page 7 of the TfL document linked upthread shows the challenge quite well. Going that deep also means it takes a long time to make the trip.
So that leaves two complementary low cost solutions, with a third in the future.
1) when Euston is rebuilt, improve the layout and public realm of Phoenix Road / Brill Place, as proposed. Excellent way finding, shared space layout, step free, better sight lines.
2) some form of autonomous pod system, using the same route, and probably at walking pace. This is a little way off, but in my opinion quite likely.
3) if Crossrail 2 gets built, use of the station as a through route. This will take much longer than either of the above, but will be possible for those that have a ticket (it would be barriered, or whatever form barriers take by then).