Class 21 and 29

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Fifty-eight Type 2 Diesel-electric locomotives were built by NBL in Glasgow for British Railways, numbered D6100 to D6157.
  • Originally all were powered by a MAN diesel engine rated at 1000hp or 1100hp. These were later designated Class 21.
  • Twenty locos were rebuilt with a Paxman 'Ventura' engine rated at 1350hp. These were later designated Class 29.
NBL/MAN D6104 on Cowlairs Incline Pilot duty, awaits departure from Cowlairs Yard, 30 November 1966 Photo by willy92140

  • There were two distinct batches of the NBL Type 2 DE locomotives:
    • D6100-37, built for Eastern Region, moved to Eastfield (65A) in 1960.
      • Red-Circle multiple working control.
      • Drop-light cab side windows
      • 'Eye-brow' cab front air vents on D6100-21
    • D6138-57, built for Scottish Region, based at Kittybrewster, Aberdeen (61B).

  • The Red-Circle locos D6100-37, built between December 1958 and December 1959, were delivered new to Hornsey, Stratford and Ipswich depots. They soon gained a poor reputation for unreliability.
  • During 1960 all 38 were reallocated to Eastfield Depot in Glasgow. (The better performing Class 26 locos moved from the Eastern Region to Haymarket Depot in the same period).
  • D6130 from this batch had been on-loan at Eastfield since November 1959.
  • After a period of storage, remedial work and driver training, they were put into passenger service, primarily in pairs on trains from Glasgow Buchannan Street station.
    • From November 1960, Glasgow Buchannan St - Dundee West
    • From April 1961, Glasgow Buchannan St - Oban (via Callander)
    • From May 1961, Glasgow Buchannan St - Aberdeen (via Forfar)
  • The locos continued to be troublesome and soon many were out of service with major engine defects.
    • Loco D6127 suffered severe fire damage at Greenloaning on 29 March 1962, while working in multiple on a Glasgow - Dundee West train. It was never repaired, but was not officially withdrawn until December 1967.
  • The Glasgow - Aberdeen expresses reverted to steam haulage from May 1962, with LNER A4 Class locos used.

  • The Blue-star locos D6138-57, built between February and December 1960, were delivered new to Aberdeen Kittybrewster (61A).
  • They mostly worked on the former Great North of Scotland lines north and west of Aberdeen.
  • They also were used in pairs on freight trains to Edinburgh.
  • Most of the Kittybrewster fleet were taken out of service during 1966.
  • The last two operational Blue-star locos D6140 & D6152 were reallocated from Kittybrewster (61A) to Eastfield (65A) in September 1967.
  • The other 18 locos of this batch were nominally reallocated to Aberdeen Ferryhill (61B) before being officially Withdrawn.

Rebuilds with Paxman engines

  • The MAN engines proved unsatisfactory, so plans were approved for locomotive D6123 to be fitted with a replacement Paxman 'Ventura' 1350hp engine. The locomotive was prepared at St Rollox Works Glasgow, with the actual engine fitted in Colchester, returning to St Rollox for completion, before beginning extensive trials from July 1963.

NBL/Paxman 6121 at an SRPS open day at Wallace Street, Falkirk in 1971 Photo by ahred05


  • Rebuilt locos (all from the 'Red Circle' batch) saw the following changes:
    • Paxman 'Ventura' 1350hp engine (except D6109 - MAN engine retained)
    • Nose doors sealed up (except D6123)
    • Four Character headcode panel fitted (except D6123, discs retained)
    • New windscreen wipers
    • Covered horn grilles on cab front
    • Extra pair of body side grilles
    • Two rotating ventilators on top of the roof
    • New livery: 2-tone green (lighter green on upper bodyside) with pale grey stripe; or from 1967 BR blue.
      • Prototype conversion D6123 had thin black stripe instead of pale grey until June 1966.

  • Differences between St Rollox and Inverurie conversions:
    • St Rollox: wider band across radiator grille.
    • St Rollox: Riveted horn grilles covers on cab front (except D6123)
    • Inverurie: Grommeted horn grilles covers on cab front
    • St Rollox: Green livery - small yellow end: rounded top corners of yellow panel, low position of BR emblem
    • Inverurie: Green livery - small yellow end: Angled top corners of yellow panel, higher position of BR emblem
    • Inverurie: BR blue livery - minimal yellow wrap round. BR symbols on cab doors, Serif style numbers.

  • Comparison between St Rollox & Inverurie green loco front ends: <Flickr>
  • Comparison between D6123 and D6130 front ends: <Flickr>

  • D number prefixes were painted out from late 1968 to 1969.
  • During 1970/71, the locos in two-tone green livery received full yellow ends (GFY).
  • The positions of 'Danger - Overhead Live Wires' signs (OHLW) varied between locos.
  • Loco data panels were added from 1969. Most locos had these on the right end cabside. <Photo on Flickr>

The Rebuilt Locomotives

Number Engine Rebuilt at Livery Remarks Date Withdrawn Photo Links
D6100 Paxman 12/1967 St.Rollox BR Blue Central BR symbol 06/10/71 Flickr 1970
D6101 Paxman 12/1965 St.Rollox 2T.Green (GFY 06/70) No front OHLW signs 03/08/71 Rail-online 1967, Flickr 1972
D6102 Paxman 06/1966 Inverurie 2T.Green (GFY 08/70) Data at left end. 06/10/71 Rail-online 1967, Flickr 1971
D6103 Paxman 10/1965 St.Rollox 2T.Green (GFY 03/71) 05/10/71 Rail-online 1969, Railphotoprints 1970
D6106 Paxman 10/1965 St.Rollox 2T.Green (GFY 02/70) No OHLW signs 18/07/71 Flickr 1966, Flickr 1970
D6107 Paxman 06/1967 St.Rollox BR Blue Cab side BR symbols 05/10/71 Flickr 1967
D6108 Paxman 10/1967 Inverurie BR Blue 01/05/69 Flickr 1969
D6109 MAN 01/1967 Inverurie BR Blue 06/04/68 Flickr 1967, Flickr 1968
D6112 Paxman 09/1966 St.Rollox 2T.Green (GFY 06/71) No front OHLW signs 31/12/71 Rail-online 1970, Flickr 1971
D6113 Paxman 12/1966 St.Rollox 2T.Green (GFY 03/71) High OHLW signs 06/10/71 Flickr 1970
D6114 Paxman 02/1966 St.Rollox 2T.Green (GFY 06/70) No OHLW signs 05/10/71 Flickr 1966, Flickr 1971
D6116 Paxman 07/1966 St.Rollox 2T.Green (GFY 05/71) 31/12/71 Flickr 1967, Flickr 1971
D6119 Paxman 12/1967 Inverurie BR Blue (extended yellow, 08/71) 31/12/71 Flickr 04/71, Flickr 09/71
D6121 Paxman 02/1966 Inverurie 2T.Green (GFY 02/70) Data at left end. 06/10/71 Flickr 1966, Flickr 1971
D6123 Paxman 06/1963 St.Rollox 2T.Green (GFY 03/70) Disc Headcode 21/09/71 Flickr 1964, Railscot
D6124 Paxman 12/1967 Inverurie BR Blue Data at left end. 06/10/71 Flickr 1971, Flickr 1972
D6129 Paxman 10/1967 Inverurie BR Blue 06/10/71 Flickr 1969
D6130 Paxman 04/1966 St.Rollox 2T.Green (05/70) No front OHLW signs 05/10/71 Flickr 1969, Flickr 1971
D6132 Paxman 12/1966 Inverurie 2T.Green (GFY 07/70) Data under emblem. 06/10/71 Flickr 1969, Flickr 1971
D6133 Paxman 05/1966 St.Rollox 2T.Green (GFY 04/71) Data at left end. 31/12/71 Flickr 1970, Flickr 1971
D6137 Paxman 11/1967 Inverurie BR Blue 24/04/71 Flickr 1968, Flickr 1971


  • D6109 was found unsuitable to receive a Paxman engine due to earlier modifications, so returned to service with a refurbished MAN engine, the only Class 21 in BR blue. It was withdrawn in April 1968 due to collision damage, and is believed to have been sold to for scrap to J. MacWilliam, Shettleston in January 1969.

  • Blue D6108 was the first NBL/Paxman Class 29 to be withdrawn from service, on 1st May 1969. After storage at Inverurie, Eastfield and Cowlairs, it was sold to for scrap to J. MacWilliam, Shettleston in June 1971.

  • Nineteen Class 29 locos survived into 1971.
  • Last four Class 29s in service were 6112, 6116, 6119 & 6133.
    • 6116 worked the 17.52 Dundee - Glasgow Queen St passenger train on 06/12/71.
    • 6112 was seen on a ballast train at Larbert on 29/12/71.
    • All four were officially withdrawn on 31st December 1971.

  • The 19 locos withdrawn during 1971 were scrapped at Glasgow Works in 1972. <Flickr>.


See Also

On Scot-Rail

Other websites:

Created by Dysgraphyk and last modified by him at 00:36, 25 of August 2025.