If you were thinking of driving solo anything like 78 miles for the first time, you'd best not. It's not because of the time or the distance in itself, it's because you will find it very tiring mentally and, oddly, physically. That presents a risk.
You have probably only driven for an half an hour or so before,
concentrating hard when you did it, and you had someone to spot trouble.
It's easy for experienced drivers because a) they usually know the route, and don't need a map or satnav or to keep looking for direction signs and b), above all, most of the time they're on autopilot; they've encountered the same problems, and spotted the potential risk that matters out of all the hundreds of things around them, thousands of times, and are not even conscious of doing it. You still have to think, all the time, about everything; your road reading is not highly developed yet. The effort tires you out.
A drive round your own patch, which you know well, is best. Incidentally, it's surprising how little you notice as a passenger; you may get lost in your own town! For a first solo on country roads, 15 or 20 miles is surely plenty. In town, if you drive half an hour it'll feel enough., certainly in London ! Then you can build as you get used to it.