Platforms != distinct rail lines. Now, if only there were plans to run a new national, let's say high speed, rail link from the North of England into Euston which would improve this capacity ...

The capacity limit is the number of tracks. There are 4 AC and 2 DC tracks on the line out of Euston and they are also used for freight trains as well as the Bakerloo line.

Heathrow has 115 gates but only does 50 departures an hour.

For a full long distance train pausing between two multi-hour trips it's reasonable.

5 Minutes for disembarking, 10 minutes cleaning, 10 minutes for boarding and you have 25 minutes platform occupancy. But on top of that the tracks will be blocked by the train going in and out for a few extra minutes, you need to find a slot on the line itself, and you need to allow for disruption.

It's all very inefficient in terms of occupying scarce and inelastic inner-city track capacity, so modern practice is to build through stations if at all possible and send trains off to sidings to be cleaned, but that wasn't practical 100 years ago.

Nobody said all problems have cheap solutions.

London bridge tracks untangled is so much better for throughput - I remember so many long waits as a Brighton train blocked the whole station crossing the tracks.

One surprising good thing the gov did at that time was insist on the rebuild of the station itself, it was particularly grim, and just a mess.

I've lived nearby the whole time and the new station is a nice space, generally efficient with good throughput for the trains.

I'm pessimistic, but really hoping they don't stick with plans to build a too small terminus in London for HS1, not too optimistic as we have Rachael Reeves as a continuity austerity Chancellor - lets see.

There were plans to expand Euston, then the Tories cancelled those plans and sold off the land that was acquired to accommodate said plans to make sure it wouldn't ever happen in the future (by this point they were already collapsing in popularity and clearly going to lose the election).