1967 Jaguar 420

When the Jaguar Mark X appeared at the 1961 Earls Court Motor Show, its impact was equal to the E-Type’s debut earlier that year. It was a frankly dramatic looking rear-wheel-drive, 5/6 seater that was the successor to the Jaguar Mk IX with de Dion independent rears suspension in a separate sub-frame (a first for a Browns Lane saloon), discs fore and aft assisted by a Kelsey-Hayes bellows servo, and the E-Type’s 3.8 litre engine. Naturally, the interior was finished with several forests worth of timber and the massive unitary body – the largest made in the UK at that time – was nearly 6ft. 5ins in width. Best of all, Jaguar’s new flagship saloon cost a very reasonable £2,392 18s 1d – a figure within reach of most captains of industry plus several leading members of the unofficial economy. The 120mph top speed especially appealed to the latter sector of the market.

Jaguar offered the Mk X with a 4-speed manual box with or without overdrive (the latter is very rare) or 3-speed automatic transmission operated by a column mounted selector lever. The engine was available in two forms - a standard 9:1 compression ratio and an alternative 8.1. Handling was enhanced by a ‘Powr-Lok’ limited slip differential. Inside there were rear picnic tables, the front seats reclined, the steering column was adjustable, and there was an elaborate vacuum controlled heating system. PAS was another, and very essential, standard fitting and the extras list included electric windows.

In 1964 Jaguar offered the Mk with the XK 4.2-litre engine (the 3.8-litre engine continued to be available until 1965) for it to compete against V-8 rivals in the US. A Girling system with a vacuum servo replaced the Dunlop brakes, and there was an alternator instead of a dynamo plus a much improved manual gear change. The automatic transmission was also uprated, and there was Marles Varamatic PAS as opposed to Burman power steering. The Mk X 4.2’s top speed was 122mph and the price was £2,156 for the standard version and £2,261 for self-selecting models.

The 1965 model year saw the Mk X available as a limousine with a sliding glass division, although Jaguar only made 42 examples. In October 1966 their flagship saloon was rebadged as the 420G (for ‘Grand’). These are recognisable via their divided radiator grilles, padded fascia, side indicator repeaters, a range of duotone paint finishes and chrome side-stripes on single tone versions. Air conditioning also became an optional extra.

During the 1960s Jaguar also experimented with a V-12 and Daimler 4.5-litre V-8, both of which were reputed to be ferociously fast. Neither, alas, entered production, but the Mk X’s floorplan did form the basis of the 1968 Daimler DS420.

The 420G ceased production in June 1970, and no Jaguar saloon thereafter has ever quite replicated its appeal.

Power for the Mk X was a 3781cc I-6 DOHC engine between 1961 and 1965 and the 4,235cc XK unit from 1964 until 1970. A Moss gearbox with synchromesh on the top three gears was used for the first three years of production, and the 4.2-litre models have an all-synchro system. The automatic boxes were Borg Warner DG for the 3.8-litre versions and Borg Warner Model 8 for its successor.

The big Jaguar is a cruising car par excellence; the manual box is actually no hardship to use, but automatic really complements the Mk X’s appeal. Although it looks – and indeed is – vast, the Jaguar has the road manners of a much smaller car and the steering is incredibly light in a 1960s Detroit fashion. Attempts at spirited cornering are often limited by the Mk X’s sheer width and the occupants sliding across the leather-trimmed benches. Some enthusiasts regard the 3.8-litre engine as more overly sporting, but all versions of the Mk X can offer magnificent motoring.

Tired rear springs, bushes and dampers are common problems on Jaguar Mk Xs and 420Gs, as are oil leaks from the rear crank seal and cylinder head corrosion. Rust can be very prevalent around the floor, suspension pick-up points and the radiator cross-member, while a tired interior can mean a huge refurbishment bill.

The Mk X was as important a Jaguar as the E-Type, not least because it established several of the design tropes later seen on the XJ-6 in 1968. And, it has a decadent charm all of its own.

Alternatives to the Jaguar Mk X and 420G include the Daimler Majestic Major, the Rolls-Royce Silver Cloud and Silver Shadow, the Vanden Plas 4-Litre R, the Humber Imperial, the Rover P5 3-Litre Coupe and the Mercedes-Benz W112 300SE ‘Fintail’.