The Secret Chocolate bar was made by Nestle in the 80's and 90's and was one of the most delicious treats ever. It had a sort of bird's nest chocolate outer with a creamy mousse center similar to the inside of a Walnut Whip. They came in a white protective card sleeve and apparently had a gold wrapper with the word Secret written on it in purple.
The television advert featured an elegant lady sat on a train eating her Secret bar 'in secret' with the accompanying music "I see her face everywhere I go... Have you seen her?..."
Unfortunately the Secret Chocolate Bar was withdrawn from sale due to the high production costs and low volume of sales.