I agree with those who say a modern 120 mm XC FS. With a dropper of course. Unless you do jumps and uplift.

I have one as my only mtb and it does everything I want. Whenever I idly browse classifieds or articles about new bikes, I never see anything that would honestly be any more capable than what I have. I do switch tyres as I have 2 wheelsets but even that isn’t really necessary.

There is the element of what you enjoy. Certainly a rigid bike or even a gravel bike would “get round” most any UK red route or bridleway. But would it be the best choice?

IMO no, but others will find enjoyment in the challenge of “handicapping” themselves in the technical sections. (And add in some tarmac to a route and it probably becomes the faster bike overall)

Really difficult to cover everything (including road) with 1 bike without significant compromise.

I think you can get pretty close to zero compromise with 2 bikes tho.

As per some of the comments above, for moderately technical XC up to DH, the sweet spot is medium to long travel FS enduro bike with 2 sets of wheels/tyres, which you swap depending on what you intend to ride.

Below that, for road, gravel, or even slightly technical XC (where you overlap into the enduro territory) – gravel bike with 2 sets of wheels. One road, one off-road.

Agree with the comments on MTB hardtails being squeezed out. I have a SS hardtail and love it, but it’s really just for when I fancy a change or for taking out in the slop when I don’t want to knacker my nice expensive bikes.
The other bikes do almost everything better. There is only one route I do regularly (classic XC with a small smattering of tech) where I think it is genuinely more fun to ride the SS HT than my other bikes.

I’d say a 120/130 down county 29er with lock out would be the best compromise but that’s just my opinion

Agree with the comments on MTB hardtails being squeezed out. I have a SS hardtail and love it, but it’s really just for when I fancy a change or for taking out in the slop when I don’t want to knacker my nice expensive bikes.
The other bikes do almost everything better.

Agree with this.
It has the benefit of comparative cheapness and reduced maintainence. Objectively, thats it.
Subjectively, many people, whether its a second bike for winter slop, or their only bike, will build one up with cheaper wear components. But thats the choice they (or bike manufacturers based on target market) make on spec, nothing to do with the hardtail configuration itself.
Not too long ago this forum beleived that dropper posts on hardtails were unneccesary. Still dont quite get that argument, but I think the crux of it was avoiding putting additional weight, cost and complexity on the “simple” bike.

Wors yeah, yeah I know 😂 and I’ve actually got 2 more. In my defence I don’t count the pub bike and I have my 11 year old Moda set up for Zwifting so I’m not counting that either, then I’ve got a Giant road bike which was my Zwift bike before the free hub went on the moda which then replaced said Giant , which is now up for sale, so I’m not counting that either!
The lad I ride with has 11 bikes so I’m actually a lightweight compared to him.
It would be nice to get down to just a road bike, an off-road bike and my Zwift bike.

just a road bike, an off-road bike and my Zwift bike.

theres another factor at play here. For example depending on where you live and if you truly only had one bike, you may dream of a weekend in the Lakes, but you spend your weeknights lapping the local flat bridleways and lanes to get fit for it… and then you find you have the “one bike” to do both of those things which is a compromise.
If the road and/or zwift bikes can accomplish one aim, your target for the “one MTB” gets easier.

I agree with those who say a modern 120 mm XC FS. With a dropper of course. Unless you do jumps and uplift.

+1

Although it comes down to £££ IMO.

A £1k hardtail and £1k gravel bike probably cover most riding better than a £2k FS XC bike. You could take the HT to BPW, and the gravel bike on an XC ride or even roadie clubrun.

But a £4k XC bike weighs as little as a £1k gravel bike and then things get a bit more blurred.

I built a lightweight ti hardtail, specifically as a “one bike to do it all”. With a choice of Sus or rigid for and two wheel sets (xc and fat) It gave great options for every occasion. Even featured in the reader’s rides bit of stw. But over the last year and with a bit of post covid traveling, I soon found out it was massively out biked at many a UK bike parks and ended up building a full sus as well.

Sooo 2 years on from building my ‘one of kind all round bike, I’m now lucky enough to have three bikes all high end, a ridgid xc fat bike – great for my local riding. A 140mm trail full sus which is great at most UK trail centres but not as good as the hardtail locally. And a high end gravel which is crap in comparison to both off road near me but much better than the other two at local road and canal path rides.

My experience is that yes you can build one bike to do it all but it won’t master it all.

theres another factor at play here. For example depending on where you live

This is a massive factor.

25 years ago, the answer was “Orange P7”.

Suspect it’s all moved on a bit now.