What the man behind today's Sac Frères hates is, 'anything endorsed by a celebrity. You see the same ones putting their names to all sorts of products and you know they don't use any of them. And my personal view is that an awful lot of so-called glamorous brands are made in a slipshod way, and I find that quite sad.'
In contrast, he says Sac Frères is, 'anti-celebrity culture. We're saying if it's a good fabric and it's well made that should be enough.'
Hence Mullen's quest for fabrics whose history is the guarantee of quality. Although not a fan of bullfighting - 'I didn't stay until the end' - the chance purchase of a matador's cape inspired him to infiltrate the closed fraternity of suppliers in Madrid and Seville, 'which took a little bit of persuading because they thought I was trying to have a go at them. But with time and patience, they were pleased.'
Next, Mullen visited the Pope's tailors in Rome, 'where they showed me all the different weights and colours of piping for different levels of Monsignors. It was extraordinary.' Papal trimmings appear on Sac Frères' range of women's evening bags. The sturdier pieces come in three sizes with modern practicalities considered, including the need to accommodate a laptop and to fit in an overhead locker.
Coming next, overnighters made of cricket-pad leather, although Wimbledon-inspired luggage will not be making an appearance. 'I thought a tennis-ball bag was a great idea until we ended up with a big green furry thing,' Mullen says.
Sac Frères has only one store, opened without fanfare last year. 'We're not racing for world domination,' Mullen says. That said, e-mails from abroad have already been received. It seems modern matadors in need of sturdy luggage are curious.