Buyer’s guide: Jaguar 420 and Daimler Sovereign

| 18 Mar 2019
Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign

Why you’d want a Jaguar 420 / Daimler Sovereign

Twenty-five years ago, compiling an article on forgotten Jaguars, I drove a scruffy red manual 420 – and fell in love.

Within five years, I’d bought my own, and I’ve never regretted it. The 420 is just so usable, so comfortable, fast and fun without being tiring.

It mollycoddles its driver with power steering, servo brakes, a magic-carpet ride and luxurious leather seats. It will swallow the family and tow a caravan or car trailer as if there’s nothing there. And it never fails to turn heads or elicit favourable comment.

It’s still overlooked – even enthusiasts, when it’s mentioned, often think of the 420G and say: “Oh, the big one.” But the 420 was the logical progression from the halfway house (in appearance) of the S-type.

It was the Mk2 cabin with the independent rear suspension and longer tail, plus MkX-style front end covering the biggest, most powerful engine to go in the compact Jag, the best brakes and suspension as well as the nicest power steering (a few had manual boxes, but most were assisted). It also had alternator charging and a powerful heater, unlike earlier models.

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
The Jaguar version was the top-selling Jag during its production life

In many ways it was the prototype for the XJ6, having most of its finest features (without the over-light rack steering), and it was the top-selling Jaguar during its short production life.

It was also the first Daimler to be powered by a Jag engine. The Sovereign, as featured, became the upmarket model phased in to supersede the Majestic Major – after the 2.5 V8 had replaced the Majestic five years earlier – and it would stay in production until ’69, because the introduction of the XJ6-based Sovereign was held up.

Rust and low values have been the 420’s biggest enemies: check panel fit carefully and use a magnet to reveal filled areas. For decades numbers have been decimated by corrosion, by robbing them of parts to uprate Mk2s, and by use as donor vehicles for replicas.

It’s still much cheaper than an S-type, let alone a Mk2, and as such represents something of a bargain – provided that you buy a good one.

Rotten cars are not financially viable to restore, costing much more to rebuild than a Mk2. Unique panels are expensive (some now have XJ6 front wing tips, which aren’t quite right) and there are numerous alterations from its sisters that can catch you out – such as subtly different door-catch positions on rear doors.

A low final drive on automatics makes then fussy on motorways, but they can be dramatically improved.

Jaguar 420 / Daimler Sovereign: what to look for

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign


See above for trouble spots

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign


The 4.2 XK is a sturdy, understressed engine fitted with twin 2in SUs. If internal corrosion is not curbed by antifreeze, waterways can clog in the block and radiator, causing localised overheating and ultimately head-gasket failure. Look for emulsion 
on oil cap and oil in water. Severe head corrosion and cracking can occur in worst cases.

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign


Worn balljoints and tired bushes (including subframe mountings) lead to soggy handling. Inspect everywhere underneath for rot, which can be severe.

Rear suspension gives a superb ride but is complex; inboard discs corrode, and calipers seize. Confirm that handbrake works well; all parts are available.


Good Connolly leather is a big bonus because replacement hide is thinner, and a retrim is costly. It’s smooth in Jag, but Daimler has perforated centre sections.

There’s less wood than a Mk2 but still plenty. Check that it’s all undamaged and matches (it was supplied in car sets) and that none is missing. Matching is tricky.

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign


BW Model 8 auto on most cars is clunky but strong; this car has a G Whitehouse four-speed conversion, which tranforms the gearing for relaxed motorway driving.


Marles Varamatic power steering was fitted on all Sovereigns and most 420s. It’s an excellent system. Any play is likely to be a worn bush: replace with poly.

Jaguar 420 / Daimler Sovereign: on the road

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
The Jaguar all-synchro manual ’box is a strong unit that’s a pleasure to use

Though the 420 is not a light car, the engine should achieve a real sensation of effortless surge under acceleration.

Lacklustre power is often caused by worn cam lobes. Listen for rattly timing chains – which may adjust out, but will probably need replacement – and for knocking, from a tired bottom end.

Oil-pressure senders and gauges are notoriously fickle, but anything less than 40psi at speed and 20psi at idle needs further investigation because it probably means that the bottom end is worn. The correct engine number starts 7F (Jaguar) or 7A (Daimler).

Slight oil leaks from the engine are hard to stem and not a big problem, but check for significant losses – especially from the rear of the unit. It may be from the oil feed on the back of the cams, though more likely is that it’s from the rope rear crank seal, which is an engine-out job to cure properly. Modern seal conversions can be fitted at the engine rebuild stage.

The Jaguar all-synchro manual ’box is a strong unit that’s a pleasure to use, especially when fitted (as almost all were) with overdrive. It’s in effect  a true five-speed that is effortless and so much more relaxing on main roads than constantly dipping the clutch to change down from fifth to fourth for overtaking.

Despite that, some people insist on fitting five-speed gearbox conversions. The Borg Warner automatic is strong, and not too expensive to rebuild. Check the fluid colour and for smooth changes (although the Model 8 is clunkier than the 35), and working kickdown. A higher-ratio diff or four-speed auto conversion is highly desirable for motorway driving.

Jaguar 420 / Daimler Sovereign price guide

  • Show/rebuilt: £20,000
  • Average: £9000
  • Restoration: £1500


Jaguar 420 / Daimler Sovereign history

1966 Aug 420 & Sovereign production begins

1966 Oct Both models launched at Paris, London, Turin and Los Angeles Motor Shows

1967 Jul Front and rear seatbelt mountings become standard fitment

1967 Aug Limited-slip diff no longer standard

1968 Jan Automatic gearbox cars changed from 3.31:1 differential to a lower 3.54 unit; ribbed cam covers replaced polished items

1968 Sep Last 420 manufactured (except South African CKD cars)

1969 Jul Final Sovereign produced

The owner’s view

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
Owner Patrick Moynihan says his Sovereign is “a joy to drive”

JEC forum leader Patrick Moynihan knows 420s better than most: “My father bought this Sovereign in 1968 when it was just four months old. He’d given up smoking 10 years before and saved the money, which paid for it! We travelled in style until the mid-’70s, by which time it was rusty and tired. In ’86 I got it MoT’d, but stored it again until my mother gave me an ultimatum in 1990: restore it or get rid of it!

“I was very lucky to buy a job-lot of spares: parts unique to 420s were impossible to find then, and still hard now. The rot was so bad it took 476 hours of cutting and welding to repair it. Rob Beere built a high-torque engine; a Harvey Bailey handling kit plus Koni dampers firmed up the handling; and an XJ40 gearbox dropped revs at 70mph from 3500 to 2200rpm. It’s an absolute joy to drive.”

Also consider

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign
Rover 3.5 Litre (left) and Vanden Plas Princess are alternatives


Buick V8 gave P5 new life in 1967, turning the staid saloon into a road burner, almost as lively as the 420. Real traditional luxury (a separate heater under the rear seat!) but a liability if rusty.

Sold 1967-’73 • no built 20,600 • Mpg 16-23 • 0-60mph 11.5 secs • Top speed 110mph • Price new £2097 (Coupé, ’67) • Price now £7-18,000


Rolls-Royce IoE ‘six’ with 175bhp gave the BMC flagship decent skirt-lifting points, but Farina hull too sober and driving experience anodine. Rare now, thanks to heroic rot.

Sold 1964-’68 • no built 6999 • Mpg 15-21 • 0-60mph 12.7 secs • Top speed 113mph • Price new £2030 (’67) • Price now £5-10,000

Jaguar 420 / Daimler Sovereign: the Classic & Sports Car verdict

Classic & Sports Car – Buyer’s guide: Jaguar 420 and Daimler Sovereign

Buy a sorted 420 or Sovereign and you can bask in the smug feeling that you’re driving the best compact 1960s Jaguar (or Daimler), for a fraction of the price of the other models.

Your family will thank you, too, as it wafts effortlessly along, lulling them to sleep on long journeys. Buy a rusty one only if you’re a DiY expert looking for a serious challenge.


  • Superb ride/handling compromise
  • Excellent value for money
  • Great performance
  • An eminently usable classic



  • Rots for Britain
  • Unique panelwork is expensive
  • It won’t repay restoration costs financially, unless you’re not paying someone to do it

Jaguar 420 / Daimler Sovereign specifications

Sold/number built 1966-’69/10,236 Jaguar; 5824 Daimler

Construction steel monocoque

Engine iron-block, alloy-head, dual-overhead-cam 4235cc straight-six, with twin 2in SU carburettors

Max power 245bhp @ 5500rpm

Max torque 283lb ft @ 3750rpm

Transmission four-speed, all-synchro manual with optional Laycock de Normanville overdrive on top, or three-speed Borg Warner Model 8 auto, driving rear wheels via limited-slip diff (later optional)

Suspension: front double wishbones, coil springs, telescopic dampers, anti-roll bar rear lower links, fixed-length driveshafts, radius arms, twin coil spring/dampers

Steering Marles Varamatic power-assisted worm and nut, 2.9 turns lock-to-lock

Brakes discs all round, 11.2in (284mm) front, 10.4in (290mm) rear, with servo

Length 15ft 71/2in (4763mm)

Width 5ft 7in (1702mm)

Height 4ft 61/2in (1384mm)

Wheelbase 8ft 111/2in (2730mm)

Weight 3668-3685lb (1667-1675kg)

0-60mph 9.2-c11 secs 

Top speed 115-125mph

Mpg 15-20

Price new £1930-2198 (420-Sovereign auto, 1967)


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