I deliberately kept my pace slow and was pleasantly surprised at the one mile mark to have done it in 11.29. It does help that the first mile and a half is down hill, on the downside it's all uphill on the way back!! At four and a half miles my right leg felt like it had come unscrewed and I was waiting for it to fall off, luckily it hung on for the rest of the run and seems ok now.
The result is I can run 10k without stopping albeit slowly and I now have a time to work on.
By the way 6.2 miles is 10k.