Building buys a pint for … Parsons Brinckerhoff

So we turn to the classic game of working out who among us has had the closest brush with fame. At first, the group is reticent. But then Rachel lets on that her “former French teacher’s cousin” is Ralph Fiennes and all hell breaks loose. Apparently Barry’s “youngest daughter’s boyfriend” is the grandson of circus master Billy Smart and Aussie Leticia claims to be related to half the cast of Neighbours.

Then Rupert pipes up – not only did his aunt present Tomorrow’s World, but he was also at university with rock band Coldplay. Impressive stuff, even if he’s blasé about it. “They’re dull, dull, dull,” he says. “Just like U2.” He gives us a little bit of air guitar here to illustrate the point.

Rachel lets on that her ‘former French teacher’s cousin’ is Ralph Fiennes and all hell breaks loose

Mike the architect turns out to be sitting on the best stories. He casually tells us he spent six months working on the film Alien alongside director Sid Mead (cue gasps of appreciation from the male members of the group) and one of his own buildings – Cardiff’s BT tower – appears in the credits of Dr Who spin-off, Torchwood. “I tape the programme just so I can see it again and again. I can’t get enough,” he jokes.

The group is divided on the merits of being connected to a programme about aliens in Wales, however. And Rachel is desperate to shake off the science fiction link. “Can you put a star by my name in Building saying ‘not a sci-fi boffin’?” she pleads.

It’s a time of transition for her. Until three weeks ago, PB’s London contingent was divided between two offices. Now everyone has been thrown together, sci-fi fans and non alike. But even if their TV tastes clash, the team has welcomed the new offices with open arms, not least from a hygiene point of view. “In the last place, we had 50 people cycling to work and just one shower. Eugh,” says Rupert. You can tell he’s a sustainability expert – he bikes to work, spent his holidays canoeing in Wales, and has a “glut of home-grown courgettes” to get through.

The group is divided on the merits of being connected to a programme about aliens in Wales

Even the non-cyclists are beaming about PB’s new home, where they have more rooms than they know what to do with. Mike floats the idea of setting up a company creche in the extra space. “All the babies could have PB-branded bibs,” he says. “It would be great for marketing.”

Rachel, who has a 10-month-old daughter, is keen on the idea. Childcare is on her mind as her teacher husband, who has been on full-time baby duty all summer, is going back to school next week. But there is a plus side to losing the live-in help, she says – “He’s going to have Liza Tarbuck’s niece in his class. Surely that’s got to count.”