If I wanted a "real" and real nice post WW II Rigby in 470, I'd buy this one first, for far less:

"John Rigby & Co. London England, Best Quality Boxlock Ejector, 470 NE.
Double Rifle. Mfr. in 1952, 26" Chopper Lump Steel Barrels, London Proofed
for 75 Grain Cordite 500 Grain Bullet. Fantastic Using Gun, that still Retains 98 % Blue, 98% + Varnish and 70, - 85% Original Case Color. Quarter Rib and Ramp Front Site. Single 100 Yard Fixed Rear Site, with 200 and 300 Yard Folding Leaf Rear Sights. Ramp Front Sight with Twilight Bead. Standard Greener Cross Bolt
Anson Deeley Action. Bushed Firing Pins, Ejectors, and Double Triggers.
Nice Factory Scroll Engraved Receiver, and Trigger Guard. Pretty Dark Grained, Checkered, Pistol Grip Stock, to Original Full Leather Cover Pad, with Matching Splinter Forearm.. Gold Oval in stock with the Letters LM. In it's Original Rigby
Case with all Accessories,
Dims Are: 1 5/16" X 2 1/16 " X 15 3/4 " LOP. 11 LBS.-5 Ozs.
Great Gun That's Ready for that Once in a Life Time Big Game Hunt!
$ 39,995"

Link is: http://www.daverifflegunsales.com/images/guns/g897.html

By the way, Dave's a nice fella to deal with, and may well deal off that price. True, its a boxlock rather than a sidelock, but so what for a great hunter. I've bought some bolt guns from him in the past and his descriptions are usually spot on.