I will here put on record my thanks to my wife Batzi for her support at the running track last year, and to Martin Fine and David Pinnick for their company on four long runs. I learned from those long runs: slow is fine and a few short breaks is fine, so long as the run is long. Come marathon day, you'll run it without the breaks. And by the way: the 'slow' and the 'few short breaks' was me - not Martin or David.
If, through running in company and allowing yourself a few two-minute breathers, you can manage two or three 20-miles-plus training runs, they will hold you in very good stead.