1931 Riley Nine Mk iv Plus Biarritz'


  • The charm and character of a rare, well preserved and original example.
  • A past entrant into V.S.C.C. Events.
  • Engine and gearbox re-built, and other mechanical work undertaken by the founder of Blue Diamond Riley Services, who owned the car between 2001 and 2008.
  • Subject to extensive mechanical work by Blue Diamond during the Summer of 2021.


Described by L.T.C.Rolt, in his book, 'The Horseless Carriage' as ' the most important landmark in automobile history during the 1920s when it first appeared in 1926, the Riley 9 broke new ground with what became accepted as the most efficient cylinder head - a hemispherical combustion chamber with large, inclined overhead valves.
During the years which followed, '9' based cars achieved many sporting successes, including the Irish G.P., the Brooklands Double Twelve, the Monte Carlo Rally, and numerous class speed records.
For non-racing motorists, the Riley 9 continued to develop. For the 1931 season, the Mark IV Plus, of which this is a rare surviving example, offered interior and bodywork
refinements, as well as improvements to the chassis, and a newly designed radiator shell. The Biarritz body was the top of the range saloon.
It is believed that, of the few hundred made of this most elegant design, only a handful remain on the road.


  • First registered in Basildon, Essex, on 2nd January 1931, so possibly built in late 1930
  • Remained in Essex until 1973
  • Owned by the late founder of Blue Diamond Riley Services from 2001 to 2008
  • Extensive maintenance invoices on file
  • Engine rebuild invoice on file
  • Invoices for £5,000 of work carried out in 2021 by Blue Diamond
  • Original instruction book
  • Buff continuation logbook
  • Five recorded former keepers from 1973 to the present
  • Road Tax and MOT exempt 
  • Original registration number


  • Beautifully patinated leather
  • Headlining clean and close fitting
  • Fuel gauge and clock not working
  • Rear luggage compartment — unusual in a prewar car
  • Jaeger gauges 
  • Good visibility through split rear window
  • Fitted carpets with rubber overmats
  • Polished wooden dashboard with diamond-shaped gloveboxes
  • Overall signs of long-term careful use
  • Steering wheel mounted hand controls
  • Pedals in the conventional arrangement


  • Steel bodied lower section with fabric covered roof and upper doors
  • Paintwork appears to be very good
  • Some paint cracking around driver’s door handle and hinge caused by slight drop of door alignment.
  • Six stud well based wheels in excellent condition
  • Tyres said to retain good tread
  • Rear mounted spare wheel
  • Single windscreen wiper
  • Underneath appears very clean and tidy
  • No reported welding
  • Flashing indicators fitted
  • Smoker’s hatch in roof


  • 1,087cc overhead cam engine
  • Singe Solex carburettor
  • Engine bay very clean
  • Manual gearbox
  • 1927 Jones Grav-Vac (Auto-Vac) petrol feed
  • Magneto ignition
  • Engine and gearbox were reportedly rebuilt in the early 2000s by late founder of Blue Diamond Riley Services
  • Manual brake adjusters within driver’s reach
  • Said to start, run and drive as it should do and brake in a straight line
  • No reported leaks or smoke
  • Said to retain its original engine, gearbox and chassis
  • No mechanical issues reported
  • Recent mechanical servicing by marque specialist Blue Diamond Ltd. in 2021


This Riley appears to be the ideal mix of originality and restoration, with its overhauled engine and gearbox to give reliable running, while the original interior exhibits the warm glow of use, built up over many decades of considerate care.
We are sure that the next owner of this Riley will be proud to display it or use it in some of the many competitive events open to prewar cars. Its originality will be appreciated by onlookers and its mechanical restoration will be appreciated by its driver.

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This item is sold on an ‘As is Where is’ basis. The condition of this item is the opinion of the seller and may differ from your own opinion. Photos and listing descriptions are for guidance purposes only*.** Car & Classic do not warrant listing accuracy. Full inspection is recommended. Viewings are at the seller’s discretion. Buyer is responsible for delivery and collection of any item purchased.

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Vehicle specification
  • Year 1931
  • Make Riley
  • Model Nine Mk IV Plus Biarritz'
  • Colour Maroon and Black
  • Odometer 17,729 Miles
  • Engine size 1197
Auction Details
  • Seller Type Private
  • Town Derby
  • Location Derbyshire
  • Country United Kingdom
Bidding history
30 bids
  • matthew•••• £15,000 20/11/22
  • edward-•••• £14,750 20/11/22
  • matthew•••• £14,500 20/11/22
  • edward-•••• £14,250 20/11/22
  • matthew•••• £14,000 20/11/22
  • edward-•••• £13,500 20/11/22
  • matthew•••• £12,750 20/11/22
  • edward-•••• £12,250 20/11/22
  • matthew•••• £12,000 20/11/22
  • edward-•••• £11,500 20/11/22

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