How many miles a week do I need to break three hours? Am I doing enough? Is 40 too few, is 60 too many? Should I be doubling up like him off Strava? Or am I just plodding about wasting months when I should be doing something clever?

It’s the question I get asked more than any other. It’s also the wrong one.

Here’s my own numbers. They’re the only ones I can swear to.

Milton Keynes 2013, first marathon, about 30 miles a week. 4:04:22, and most of that walking.

Manchester 2014, 40 to 50 a week. 2:55:02.

Manchester 2016, 90 to 110 a week. 2:45:49.

Look at that again. Thirty miles to forty-five bought me an hour and nine minutes. Doubling again, forty-five to a hundred, bought me nine. Nine minutes, for twice the work. The returns don’t taper off, they fall off a cliff.

What sub-3 actually takes

6:52 a mile. Twenty-six times. Plus the bit at the end nobody warns you about.

For most people that’s 45 to 60 miles a week, held for twelve to sixteen weeks. I did it off 40 to 50. Plenty do it off less. Some need 70.

It varies because mileage isn’t what makes you faster. It’s standing in for what does, which is how much aerobic work your body can take on and repair. Two runners on 55 miles can be doing completely different training.

Three things that matter more

How long you’ve been at it. Forty miles a week for three years beats seventy for ten weeks. Every time. Heart and lungs come round in weeks, tendons take months. That gap is why people who ramp up fast get injured while their legs still feel great, right up until they don’t.

My 50 to 100 build ran November to January. I didn’t smash 90 in week one. Bit by bit, let everything catch up, and by January 100 felt easier than 50 had the year before.

Whether your easy days are easy. This is where sub-3 chasers come unstuck. Plod round at 7:45 because it feels alright, turn up Tuesday too knackered to hit the paces that would have made you quicker. If your easy pace and marathon pace are within ninety seconds of each other, you’re not running easy. Slow the easy down and the hard gets harder. That’s the whole trick and it’s free.

Whether you finish long runs strong. Hull 2015. On for sub-3, crumbled at 13 miles, 7:00-plus pace all the way in, feeling like death. Hull 2016. Set off steady at 6:50, ran straight past the spot I’d fallen apart, sub-6:00 miles in the last 5k. 2:51:01. Sixth, from thirtieth at mile six.

Same course. Same runner. Twelve months. That wasn’t a session, that was endurance.

Working out your number

Start from where you are, not where you’d like to be. Average week over the last three months. Not your best week, the average. It’s lower than you think.

• Add ten per cent every second or third week, not every week
• Sit at each level a fortnight before adding again
• Every fourth week, drop back a quarter
• Anything hurts more than three days, stop adding and hold

From 35 miles that puts you at 55 in three months, comfortably, tendons along for the ride instead of quietly falling apart. That’s a sub-3 build.

The bit nobody wants

The runners I coach who get there are almost never the ones asking about mileage. They’re the ones turning up for eighteen months of dull, sensible work without missing weeks. There’s no secret in it and there never was.

Progress is boring. That’s exactly why it works.

Miles make champions. You’ve just got to give them long enough.

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Rather not work it out yourself? My personalised training plans are built off your own recent times and written round the days you can actually train. Or if you want it changing week by week as life gets in the way, that’s what one-to-one coaching is for.