Warm up and warm down

Ashamed to be asking such stupid questions but here we go...

All of the speed and pace sessions in the RW 1/2M schedule specify a 10min warm up and warm down. But when I'm trying to run before work and get to work on time, or do an 8mile run after work, I don't always have time to do the whole 20minutes.

So my questions are: what purpose do these serve? Is the extra mileage they add of any importance? does it matter if you reduce/miss them?

Obviously, some form of warm up is important especially before the speed sessions, but I'm less sure about before pace sessions or the warm down.

Thanks,
Doobs.

The warm up is to, as the name suggests, warm up the muscles to get them ready to work, if you don't have time to do 10 mins then do a gentle jog for 5 and some light stretches the same after your workout, a gentle 5 min jog to get your heart rate and breathing back down and always do stretches after.
If you miss these parts of your workout you will probably find you feel very sore after a while, your muscles get tighter and you will probably end up injured, frustrated and annoyed that you didn't take some advice to heart.
Good luck with the half marathon though.

Thanks Sarcy1

That's pretty much what I had assumed but noice to have confirmation. I do always stretch afterwards which I find helps to keep my dodgy knee in check.
Doobs