Pruning apple tree advice neede

The honest answer is that the tree has been neglected and is now a difficult shape. It will take years of dedicated pruning in the right way at the right time (including some summer pruning).
What you prune off, it will grow back in an even more tangled mess next summer. If only there were a few more lower branches to absorb the energy coming up from the roots, then it might be possible to get it to shape-up nicely.

Of course, how and where to prune depends on what shape, height and spread you want it to become.

Easiest options are to just accept it as it is, or get rid of the tree and plant a new one in a different spot (to avoid replant disease) that gets trained and pruned properly from the start; better to do it right from the start than to try to put it right years later.

As it's winter you can probably prune it almost anywhere you like. But you may get little or no decent-quality fruit for several years.

If the tree is a particularly rare or special one, I would be more sympathetic and might be prepared to spend a lot of time examining pictures to see what could be done.
If you're not too far from me I might be able to drop in and take a look - maybe prune it for you.

Thanks for the offer of coming to take a look FB. I'm near to Southend, Essex so a big distance from you.

I'll be doing this as a favour for an elderly neighbor, the "Brief" is to reduce the height of the tree, getting rid of it is not an option, it does produce a good amount of fruit.

From what I've read, 30% is a safe amount to prune in one go, it's just which 30%?

I was going to reduce the height now, trim off the very low growth and then do more next year, so any advice base don that would be helpful.

TIA - JD

The trouble is, hard pruning (anything more than about one-tenth of its mass) will see fruit production and quality plummet. The tree may abort the blossoms, may drop the fruits, and the fruits which remain may be riddled with bitter pit.
The hard pruning you want (and need) to do runs a high risk of little or no good fruit for a few years.

Yes, you can prune off 30%, but that will be mostly at the extremities where all the fruit buds will be (fruit buds will be most numerous on the most sun-exposed areas).

I think whatever you do, after a single pruning it's going to grow back looking even worse than it is now.
If you're really determined you could bring it back into cropping if you're prepared to see the project through for about three years (about six bouts of pruning in total - including careful, skilled summer and winter pruning; not just hacking at it).

With the tree being very one-sided, there's a good chance that it's going to gradually lean more and more.

If you're prepared to commit to pruning it carefully several times, then post some more (zoomed-in) pictures of the lower half of the tree from different directions (between the lowest branch and where you've put the blue lines). That will make it easier to see what there is to work with lower down.

But I still think the easiest option would be to get rid of it and plant a new one which will look the part straight away, won't require the time and effort, and will be in full cropping before this neglected one.

Actually - the easiest option would be to do absolutely nothing and leave the tree unpruned so that at least its fruit quality and quantity won't be affected (since you say that it produces decent amounts of good fruit).