Looks like a wallflower to me, Erysimum species. have a smell of the flowers, especially when the sun's on them.

Yes its a wall flower,
reminds me of the school dance "and the days i was a wallflower, couldnt dance wouldnt dance hence you we're called a wall flower,
The other thoughts ref this plant is the sunday morn visit to the cemitary, it was the wall flower that was the excepted flower to be seen in such places,

Ive a bed of these mixed with tulips i planted last year ,
the wall flowers have just come into bloom along with the tulips, looks really nice,

Some people think the wall flower is an annual plant but in fact if you leave it in its flowering possition it'll flower year after year,
ive a very small fron bit of a bed and its got wall flowers in now that have been there for 3 years.

I agree that the wall flowers sold as annuals will flower for at least 2-3 seasons.

There is also a perennial wallflower . One ,called Erysimum "Bowles Mauve" holds the record for constant flowering in my garden.

It flowered constantly for 19 consecutive months! It was hit hars by a frost about 6 weeks ago and briefly stopped flowering but it's in full flower again now

http://www.flickr.com/photos/31559373@N00/7032820087/

Hi Anchorman?
Its like geraniums, show can buy a variety that last for years and is hardy to most uk winters,

Most people who go to the garden centre'e never look at these small plants because they look like weeds but once planted outside and fed they grow to a good spread and flower all summer, die down in the winter and re-appear again next spring /summer.
Ivz four in our garden and all are shouwing signs of doing well.
The lupin is another nice flower but only last a short while but if you cut it back after the first flowers had gone you'll get a second showing late summer & if you keep the seeds and sow next spring you'll have even more lupins.

Thanks everyone.
To support what others have said, this is the 3rd year that I've had this garden and I never planted the wallflower. So this is at least the 3rd consecutive year that it has bloomed. And hopefully it'll bloom for many more years to come. ;)