What's all this about?

First, we had the mighty McLaren F1 Longtail (LT). Then the Surrey-based company revived those two evocative letters for the stupendous 675LT, which evolved into an open-top 675LT Spider version. Then the 600LT Coupe arrived... so can you complete this sequence and tell us what comes next?

Ah. At last! We've got news on the new Toyota Supra?

There's no need to be facetious. As you are no doubt fully aware, you're looking at the McLaren 600LT Spider. Like its fixed-roof sibling, this latest addition to Woking's LT canon will be built in limited numbers, although there is no value for precisely how many will be hand-assembled at the factory. Instead, all examples of the 600LT will be built in and around other Sports and Super Series models, as and when interested parties stump up the £201,500 required to secure one unit of this newest Longtail.

Cor, that's a lot of cash! What do I get for my money?

A bloody ballistic convertible, is what. Such is the toughness of the 600LT's inherent structure, based on the carbon MonoCell II tub, that no additional structural bracing is needed for the Spider. Thus, at 1,297kg, it's 50kg heavier than its Coupe relation (that gain all brought about as a result of the roof's mechanicals), but - thanks to carbon-fibre bodywork - it's still 100 kilos trimmer than the 570S Spider that sits one rung down the McLaren ownership tree. Possibly in a web, or something. Anyway, this kerb kg figure results in a power-to-weight ratio of 463hp-per-tonne.

*Does some quick, rudimentary maths on a calculator* So it has, er... 600hp?

Um, yes. But you didn't really need to work that out, as that's what the '600' in its name stands for. However, just to confirm, the 600LT Spider has the 600hp/620Nm derivative of McLaren's mighty 3.8-litre biturbo V8 stashed in its midriff, driving the rear wheels via a seven-speed SSG transmission. Performance is barmy - 0-62mph takes 2.9 seconds, 0-124mph takes 8.4 seconds and, flat knacker, the 600LT Spider will hit 196mph. Fear not if you're wondering why it can't crack the magic double-ton, though, because that's the limit with the roof open - with it closed, the Spider will scuttle its way to 201mph.

Otherwise, mechanically it's the same as the 600LT Coupe?

Yup. Same fixed rear wing, which conjures up 100kg of downforce at the steady speed of 155mph. Same Pirelli P-Zero Trofeo R track-focused rubber. Same hugely advanced suspension and internal-organ-rearranging brakes. Same everything, really. Only you can enjoy the sunshine a little bit more, while you're driving it.

Any more details on the roof itself, or the interior?

On the former score, the 600LT Spider has a three-piece, electrically powered retractable hard-top (not fabric), which can be operated at speeds of up to 25mph. It stows behind the rear seats when the cabin is open to the elements, but the recess the folded lid sits in for top-down driving can alternatively be used to store 52 litres of stuff if the roof is up. A glazed wind deflector can be raised or lowered independently of the roof itself, while the interior is lifted wholesale from the 600LT Coupe; so there are Alcantara-clad lightweight carbon seats from the P1 hypercar as standard. Or, if they somehow don't fit the bill, then you can opt for the Senna's pews instead. Finally, if you want to go 'full lightweight', then there's the choice to delete the audio and climate control systems to pare further kilos from the Spider's svelte frame.