Euston 1960 (from Warrington). First trip on a long-distance train.
Told to use the Northern Line to meet my brother at 1800 on a Friday at the top of the steps at Strand tube station (now Charing Cross).
It worked, despite the crowds!
Euston was big, grimy, old-fashioned and confusing, ready to be knocked down and rebuilt for electrification.
I can't remember the traction, but most trains were still steam-worked at that time.
I do remember the Board Room and the Robert Stephenson statue, and the famous arch outside (which served no useful function, and just got in the way).
Returning north on the Sunday, we crossed the newly-opened M1 instead of running alongside it, which must therefore have been my first Sunday diversion off the main line via Northampton.
A year later, I first used the Circle line from Euston to Paddington to reach university in Reading, and it became a regular journey for me.
Paddington was quite different in character, but just as grimy.
In those days, I usually battled up to Euston through the electrification works behind an EE Type 4, often hours late on a Sunday.
Returning north on a Friday, with few WCML services I mostly used the Midland route to Manchester Central, on the 1425 from St Pancras, calling only Leicester, Derby and Miller's Dale.
Always a pleasure to leave St Pancras behind a Peak, especially the climb from Ambergate over Peak Forest and coasting from there all the way to Didsbury or beyond.
It took me a long time to find the other London termini, and even today they seem "foreign" to me.
I think Fenchurch St was the last one I discovered, and that was only to complete the set!
I did manage one trip on the Marylebone-Manchester sleeper via the full Great Central route, before it was axed after full electrification to Euston (steam to Nottingham Vic, EE Type 4 beyond).
Also one trip on the Paddington-High Wycombe-Birkenhead route (I lived on the Wirral then) before it was downgraded, also after Euston electrification.
Reading-Oxford-Banbury-Birmingham, which you might think was the natural route north, had an appalling service then, usually needing 2 changes (Oxford and Banbury) and using stoppers throughout.
Only one train ran through, the Paddington-Birkenhead sleeper service, which was the one train not diverted via High Wycombe when the shorter route opened.