Please could somebody tell me what the flower is? It is in my garden
Looks like a seedling of oil seed rape to me. Have you got fields near you?
If you haven't got rape fields nearby it's probably charlock, which used to be a very common arable weed before herbicides were used.
Charlock for me - rape leaves are smoother.
We have poppies there is a hedgeway near a rail track I really like wildflowers to go with bees and butterflies.