What is this ?

[macmac]

This pretty flower appeared next to the water trough on the lottie last year and has reappeared this year.No one there seems to be able to identify it.
do any of you flok recognise it ?

[macmac]

[triffid]

It looks like watercress in flower to me. .. which would make sense of it enjoying life by the water trough. Will try to find a piccie.

[Jayb]

It looks like Lady's Smock to me, very pretty.
http://www.healeydell.org.uk/files/Ladys_Smock.pdf

[OllieC]

It looks like Lady's Smock to me, very pretty.
http://www.healeydell.org.uk/files/Ladys_Smock.pdf

Yes, Lady's Smock, and yes, very pretty.

[triffid]

Actually, at second squint, it might be hairy rock cress or thale cress. It's hard to tell without seeing its leaves.

Hairy rock cress: http://calphotos.berkeley.edu/cgi/img_query?seq_num=276315&one=T
Thale cress: http://en.wikipedia.org/wiki/Arabidopsis_thaliana

Well at least everyone's IDd it as a brassica.  ;D

[Digeroo]

What about white hesperis (sweet rocket) does it have a nice smell.  I presume the leaves we are seeing is grass.  Did someone spill a packet of seeds? 

Watch out it is terribly invasive.  Make sure you remove the seed heads.

http://www.dianeseeds.com/files/hesperis_matronalis_alba.jpg

If it does not smell sweet then I would suggest white honesty.  In the garden mine look more like yours than the picture link below, the leaves are far less noticeable near the flower head.

http://www.photoready.co.uk/flora-fauna/images/white-flowers.jpg

[worldor]

Whatever it is its beautiful. Wouldn't mind it round my lotty.

[macmac]

It looks like Lady's Smock to me, very pretty.
http://www.healeydell.org.uk/files/Ladys_Smock.pdf

yep on closer inspection I think that's what it is  thanks folks  :) :) :)