[Mark's Sussex Allotment]

My peas emerged nice and quickly and then grew well, but when they got to about 3 inches high they all have been set back and eaten/nibbles by something.

Any idea what this could be and what can I do to prevent it?

[Chrysalis]

I think it's sparrows!  pesky things.     I've netted mine and got lots of twiggy stuff/mesh etc. to deter them... Still some nibbled bits though.

Hope you can save some peas....

[mumofstig]

Or could be pea and bean weevil.

Adult pea and bean weevils (Sitona lineatus) eat semi-circular notches out of the edges of the leaves of peas, broad beans, clovers and vetches. The weevils can occasionally transmit mosaic virus of broad beans.

http://www.gardenorganic.org.uk/factsheets/pc25.php

if it's these the plants just grow through it 

[solway cropper]

Young pea plants are gourmet food to sparrows. I have an 80 foot long hedge down one side of my garden which is home to numerous sparrows and I have to adopt the same tactics as chrysalis if I want a crop at all. Once the plants really get going it's not so much of a problem but they do need some protection early on.

[Li]

I had this last year and it was weevels they loved peas and my broad beans only till they were off the ground as much to say 

[Chrysalis]

So sparrows AND weevils.  Lucky you! 

Good luck with your protection strategy..