140 miles in one day?

Im plannin on cycling from london to Hemsby in Norfolk (Great Yarmoth). Going on google maps and clicking 'avoid highways' tells me that its around 140 miles. I was hoping to do it in a day (gettin up eeearly). recon its possible fixed? dont think the routes too hilly and i like to think im pretty fit, ride every day around 8-10 miles, but it will be my first real trek. will it happen?

I did London to Wells-next-the-Sea (about 140 miles) with gears a couple of years ago and then came back the next day. It was OK, though I was ready for my tea at the end. The flatness was what made the difference. Wouldn't much fancy doing it fixed, though.