False critical alert from Apple - scam and/or virus??

A couple of days ago whilst browsingthem web ( English version of large, reputable German company) I received a pop up alert stating " Safari Alert , your iPad is locked for your protection call Apple Support on 0808 148 3688

I got my Son to look up Apple number on his mobile and realised it had nothing in common with the number above . As IPad was frozen I did a forced shutdown athe following that did a soft reset not had to reset wireless connection but did not wipe off any personal data and after this the pop up disappeared. My device is an unsupported Gen 1 iPad iOS 5.1.1. My question is how can I tell if my iPad has a virus and/or is safe to use? Also, I assume due to being unsupported its pointless my calling Apple? Any advice appreciated - other than telling me to buy an updated IPad which Unfortunately I cannot afford (this is first use since problem occurred)