Am I being scammed? Does Yahoo sponsor a lottery awarding X amount, British Pounds to randomly selected users?

Genuine/Scam. I am wary of "award notifications" via email but I would hate to miss an opportunity if this notification is legit. Can anyone tell me if they have received similar "prize notification" email? If so, I know this one is bunk. If I do not get any answers I still feel like I should be cautious. It says I must keep mum about the notification or I will forfeit my winnings. Did I just blow it? Am I missing an opportunity by playing it safe or should I respond? Please advise. Thanks!!!