It’s apparently a well known scam originating from USA. I found some stuff on the interweb about it and reset Safari as suggested. Nothing was downloaded I just used the reset feature on the tablet, and hopefully I have disposed of it. Fingers crossed it doesn’t come back.

It will offer you a free card containing some sort of cash inducement if you fill in your details. I assume that none of us is stupid enough to fall for this, but forewarned is forearmed.