A couple of years ago I covered some nice amateur snapshots of HMS Campania here, the escort carrier converted to serve as an exhibition ship for the Festival of Britain in 1951. Today we have an official postcard of the ship:

At first glance the ship looks much as she did as an aircraft carrier, with only the rows of flags on her flightdeck:

And the words ‘Festival of Britain’ painted on her hull showing her new role:

The actual changes to the ship were, however, a little more complex than bunting and paint, as explained by the Daily Mail in 1950:
Conversion of the 16,000 tons aircraft carrier Campania into a Festival of Britain Exhibition ship begins this summer. It will be ready for displays by the autumn.
In the 300ft long hangar galleries will be built to add to the display area. The flight deck will carry open air exhibits, including motor boats and yachts, and there will be an area for recreation and amusements.
Amidships, a large awning-covered space will house demonstrations and sports displays, and the forward part of the flight deck will be used as an open-air cafe.
Hello again,
You’ve covered this vessel’s role as the touring Festival of Britain a couple of times now so I thought you’d be interested to see this programme currently up for sale on ebay:
https://www.ebay.co.uk/itm/1951-Festival-Britain-SHIP-CAMPANIA-brochure-rare-adverts-Illustration/274279813906?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160727114228%26meid%3Dbeeff24c61174eee92ab664a04304c4e%26pid%3D100290%26rk%3D3%26rkt%3D4%26sd%3D164141587069%26itm%3D274279813906%26pmt%3D0%26noa%3D1%26pg%3D2060778&_trksid=p2060778.c100290.m3507