I shot this picture at Jaguar’s Castle Bromwich plant last week. On the left is a rear door from the new XJ saloon. On the right is a rear door from an XF saloon.

This little hands-on demonstration was designed to show us just how much weight can be saved through the use of aluminium. The XJ door weighs just 8.9kg, while the XF door weighs 13.9kg. That’s a massive 5kg saving, making the XJ door nearly a third lighter.

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What struck me straight away was the seemingly comparative ease of fitting aluminium doors to the rather weighty XF saloon. I suppose if we have four doors the total weight saving would be 20kgs, and we could deduct another 25kg by using an aluminium bonnet and boot lid.