Once I got it downstairs I set about doing a dry run to makes sure everything was going to glue ok. There no second chance once the glue is applied. Luckily everything did and I clamped it up and left it over night.
Once I'd roughly cut the top out with a jigsaw to a 54cm radius I set out to give it a decent flatten. It had a slight crown in the middle of the top surface and corresponding cup on the underside. I wasn't looking for perfection, after all it's somewhere to eat dinner and not a reference surface. You can't plane with the grain as the surface doesn't have one grain orientation but instead you have to go 90 degrees to it. A sharp jack plane did a very good job of this and after a couple hours I had it flat and thicknessed.
I made a trammel jig to hold my 1/4" router and set the radius to 53cm and slowly worked my way round the table. The router isn't big enough nor powerful enough for this job but I got I done eventually. The underside was given a 45 degree chamfer and the top a round over.
I have a Makita 1/4 sheet sander but it's not really up to the job for something this size. I decided to splash out on a new random orbit sander. This one can use both 125 & 150mm discs. I can't believe how quiet and vibration free it is. A couple of hours was all it took to get it sanded up to 240 grit.