To Paris in June, where the local branch of the auction house Sotheby’s held a sale of 260 pieces of comics artwork, including samples from the likes of Jim Lee, Hugo Pratt and Uderzo, with a total sale value of €1.3 million.

The manga component was only a small fraction – largely from Osamu Tezuka. Notably, the Tezuka pieces sold at the low end of their expected price, suggesting that Sotheby’s assessors, whoever they were, had rightly predicted their likely value. Your mileage may vary – none of them looked particularly interesting to me. Astro Boy et Autres Personnages, for example, which went for a posh-sounding €3,625, was a scrappy little pen-and-ink study of five unrelated Tezuka characters. What you were paying for was largely its provenance, which is to say that value of knowing that these images were drawn by Tezuka himself, who is too dead to draw any more.

Most surprising was a single head-shot of Dragon Ball’s Son Goku, drawn by Akira Toriyama, which went for €15,000, five times the estimated price. Toriyama is still happily alive, and is presumably cackling to himself in his studio as he knocks out another hundred such sketches to put on eBay. One suspects that Chinese capital is at work here, bidding up the value among people who have read the manga in Mandarin.

In the meantime, here are my top tips for anyone seeking manga artwork as an investment.

Make sure it’s signed clearly, and preferably not to you. Future buyers will want the artist’s signature, not the fact that it includes the message “GEMMA YOU ARE TOPS!” Not unless their name is Gemma – a limited crowd.

Try to get a single study (a bust, full-length shot or face), not a random collection of heads; it’s worth more if it’s hangable as a portrait.

Beware of gimmicks – Motoko Kusanagi depicted as your girlfriend might feel like a giggle today, but only if you become as famous as she is.

Do think, too, about the capital you are already investing. If you’re spending £10 for the sketch, and giving up two hours in a line, and a weekend at the convention, and the train that got you there, the incidentals do mount up. Has it really cost you £10, or has it already left you £200 out of pocket? Because not every queue is going to be worth standing in.

Jonathan Clements is the author of Anime: A History. This article first appeared in NEO #153, 2016.