First off this is almost completely my fault as I never used to bother separating my washing - I have learned now.
Anyway, I could really do with making my white tops whiter as they are faded and grey, one even is slightly yellow in colour
I did a wash with Dylon's 'whitening' washing machine powder, which did absolutely nothing.
So I tested soaking a top (I chose the oldest one, just in case) in a tub of bleach overnight and it didn't do anything either, in fact if anything I think it went slightly yellow.
What works? Please tell me there's some magic cure?