A free training plan can be a great place to start. There are lots available, but these16 week training plans are all available from the Runnersworld website for free:

• Get around - A beginner’s programme, mixing some walking with running, over 4-5 days a week.

• sub 5 hour marathon - to break five hours, you should eventually be capable of a sub-2:15 half marathon (10:15 per mile) and sub-60:00 10K (9:30 per mile). Right now, you should be used to running comfortably for 30-60 minutes, three or four times a week.

• sub 4.30 marathon - you should be capable of running a sub-2:00 half-marathon and a sub-53:00 10K.

• sub 4 hour marathon - To break 4:00, you should eventually be capable of a sub-1:50 half marathon (approx 8:20min/mile) and a sub-50:00 10K (approx 8:00min/mile).

• sub 3.45 marathon - To break 3:45, you should eventually be capable of a sub-1:45 half-marathon (8:00 per mile) and sub-46:00 10K (7:30 per mile). Right now, you should be running at least 25 miles per week, and be able to run for 1:15 non-stop.

• sub 3.30 marathon - You’ll need to be pretty used to running several times a week, as this plan builds up from 44 to 60 miles, training over 6-7 days.

• sub 3.15 marathon - To break 3:15, you should eventually be capable of a sub-1:30 half-marathon (6:52 per mile) and sub-40:00 10K (6:30 per mile). Right now, you should be running at least 30-35 miles per week, over five or six sessions.

• sub 3.00 marathon - To break 3:00, you should eventually be capable of a sub-1:25 half-marathon (6:30 per mile) and sub-38:00 10K (6:00 per mile) Right now, you should be running at least 35-40 miles per week, over six or seven sessions.