The boss tried to tell us that it was illegal for us to discuss who we voted for; I had to explain to him that it was not illegal for me to tell you, it was illegal for him to demand that I tell him...
Padre is exactly right. Here (and I suspect in the UK as well) the secret ballot is a right; not an obligation. If I choose to waive that right and tell people how I voted, it's entirely legal.

“Life is a whim of several billion cells to be you for a while” ~ Groucho Marx