Could I run a marathon

Probably.  You should try running 20 miles to see how to feel at 19.

How long is your usual long training run? I think you would get around a marathon but might find it quite painful if you aren't use to long training runs!!!

"Also I really can't see myself just going out on a training run of more than 2 hours but would run for longer in a race."

Based on your Bewl 15 mile result, Mcmillan would indicate a marthon time of 5:34 if you trained for the distance. From what you wrote, you do not seem keen on undertaking a marathon training plan which would have several runs in excess of 2 hours.

If you don't train for the distance, you may probably still get round, but it is likely to be a memorable experience for the wrong reasons.

I would look through some of the training plans on RW to see what you should undertake as part of the training, then decide if the distance is for you.

Hi Also-ran  - can you confirm the calculation for Bewl 15 vs full marathon time ?

Bewl 15 in 2:09          full marathon time of 5:34  ?

- Just rerun the figures and it looks to be 3hr 54 min

Sorry - copy and pasted wrong thing : 3:54:38. Should have been obvious to me (that would have been some fade ).

What concerned me more was the relucatance to train long. Now  we are looking a 20 miles which is still a lot further than previously run, and there is only a handful of weeks left to Sept 9th. Its not enough time to train, recover and adapt to longer distances. While the distance can be done, its going to be more of a learning experience  due to the time constraints.

J1M , if you are going to be doing it, personally I would forget about intervals for now. Long Slow Run at weekend, medweek longish run(10+), and if you are up for it, a tempo run. Otherwise, easy/recovery runs.

J1M. For the weekly mileage you are doing, I wouldn't do two hard sessions in the week. Do one at most (tempo or hills). 9th Sept is not so far away, and you need to save your best for then. I think you will benefit most from easy aerobic running . A big risk will be increasing your weekly mileage by too much, so I would keep the intensity down, and maybe just stick to the short tempo session for speed.

I generally do either my long run and/or midweek long run on terrain specific to what you are racing on. So if it is undulating or hilly, then that will give the best preparation (but run it slow!)

I'd not do a marathon off half marathon training unless I'd had some longer runs in the recent past.

Half marathons are easy. Running past 20 miles is a hell of a lot harder - you really need the long runs. Really. 

J1M - not sure why you are bothering to enter long races if you don't like long distances and can't afford the time in training. Doesn't make much sense to me.

Also, be wary of confusing the terms 'fitness' with 'endurance ability' or stamina. They are not synonymous. You train differently to achieve stamina (performance over time). The kinds of distances you have been training so far wont do a great deal to improve your stamina, so i think you are right to avoid doing very long races.

Cheers and good luck, TD

in answer to your original question.  you probably are 'fit enough' to complete the marathon.  you might be able to complete the distance but you dont know what it has in store for you after 15 miles.  it really makes sense to get up to 20 miles+ in training.  i have done this every time i run a marathon and still find the last 4 miles really tough.  you dont want to have to endure this for 8-10 miles.

Also i agree with tricky dicky, if you are not interested in running long distances in training, why bother race them?  Some of the fastest distance runners at my club (and in the region) have no interest in running beyond 13 miles or in some cases 6.2miles.  they can run 31 -32 min 10k's as that is what they train for.  everyone thinks that completeing a marathon is what makes you a 'proper runner' but there are plenty of hard core runners who have not completed anywhere near this distance.

Good luck in the 20 mile race, i dont think you will have a problem completing it.  you may find it tough but you should be fit enough to finish.

I don't know if you're familiar with the terrain of the DD20 but don't be too put off by the uphill start.  It levels out to give your legs a rest, but take it easy getting up there.  Rolling back down at the end is fun, if you've got any quads left.  I "won" this event three years ago in prep for the Beachy Head marathon, but it's billed as a "challenge" rather than a "race", so don't kill yourself trying to get on the podium.