I read a book around 1998-2000, which was about a group of (U.K./English?) scientists who had created a time machine.
One of them, a female, travelled back in time and arrives in the time of the Vikings.
She falls in love with Per, who I think was the Viking king or perhaps the prince.
I can't remember the name of the author or the book, and I'd love to find out if anyone knows/remembers this book!