Presumably the other side of the planet blocking the sun's rays?
I've read here multiple times that a "small" solar farm in the Sahara desert would suffice to provide energy for all Europe. Even if you can solve transporting it, imagine what could happen if it's in, or the wires run through a country in civil war, like Sudan.
There's a project that's planning solar power generation in Morocco and a cable to the UK. That'll be a fairly long cable. https://en.wikipedia.org/wiki/Xlinks_Morocco-UK_Power_Projec.... Though no idea how realistic this is, it seems a bit like a new electric car company website that only has a prototype. Meaning, it seems that project seems to not escape the planning stage.
There's already a lot of cables between the UK and other countries, e.g. Norway and France. Though those aren't that long in comparison to something connecting to the UK.
EU is trying to tie all the various grids of the various countries together. There are loads of initiatives around that. Aside from that the Southern EU countries are trying to connect their grids to North Africa. Though again, that's not a huge distance to cover.
They promise to start delivering power in 2030, and estimate the project cost at 16bn dollars or something along those lines.
We all now how well it goes with mega projects :)