You can if you do it at a roadside CP, and inform the marshalls of what's happening! I got slowed up massively over Fleet Moss a couple of years ago, ended up having to take someone BACK to Fleet Moss checkpoint (panic attack in the dark/bog!) then rejoin a later group as all bar me of the original group threw the towel in at that point. Then most of the second lot jacked it at Cray so I had to wait again...
...eventually, we got timed out at Park Rash. A lesson learnt, that year!