Aluminium version of the Deluxe Porteur Rack from SOMA Fabrications. The rack has a 12 x 14.2″ platform with a max load of 10KG.
It has attachment points for mini rack eyelets for added stability and safety also the rack is height adjustable. Mounts to the axle, but there is a workaround if you want to attach it to a fork eyelet.
The horizontal strut under the platform will fit a Zimbale or Carradice roll bag and perhaps a pannier with narrowly spaced hooks.