Laying outside

Hello
My son got a lovely birthday present today, Gwendoline laid her first egg
She's happy to sleep in the nesting box (when I forget to close it off) but laid her egg outside under the house.
Any idea's how I can encourage her to use the nesting box, it has 'fake' eggs and is clean, dry and warm(er). Definitely no mites
Thanks Jo 

 
I had one do this for a few weeks!! After week one - she would go in and think she had laid!!! When back outside and "recovering" from laying it would drop out!! Or if you made her jump.....as she ran off it would come flying out!!! 
She always lays indoors now tho!! 

Thanks for replies
She did it again yesterday, when I checked the nesting boxes they had obviously been disturbed. So its probably like you say she hasn't quite got the hang of it yet
We haven't had any eggs for a couple of months now as we lost all our layers to the dreaded fox. All the younger ones were still cooped up and safe at the time so at least we didn't lose all our hens.
Im looking forward to egg on toast for breakfast now
Jo