Gill Sans.

It's not like you to slip up like that Jan - that's not Gill. The R has a straight leg, and the stems look a bit tapered.

Ooops. Sorry.

A short G-search (in Dutch) digs up this:

Voor de typografie van de naam Graphic Design Museum is gekozen voor een Nederlands letterontwerp. Luc(as) de Groot (Fontfabrik) is de ontwerper van de TheSans, de schreefloze versie uit de TheThesis familie. Dit lettertype wordt veelvuldig gebruikt voor corporate doeleinden over de hele wereld en staat als zodanig voor wat het is. De uit TheSans getypografeerde naam in het merkbeeld is door Luc(as) de Groot in de subtiele details gemodificeerd.

Ergo: a modified TheSans — mod by its creator Luc[as] de Groot.

Add: The last sentence in Dutch is something like — De TheSans based typographic name in the logotype has been modified in its subtle details by Luc[as] de Groot.

Without being able to say what it is: It’s not a modified TheSans. None of the characters comes even close to the retail version. Only the heavy ‘B’ on the left-hand side seems to be taken from TheSans. And there is a different version with TheSans: http://www.frederikdewal.nl/Graphic-Design-Museum-Beyerd-Breda.php

Oww, sorry about my call on this. Shows that you just can’t believe what’s written on that thing called the Internet...
Taking a closer look at the image I’d say it is a modified Gill Sans (or any of its lookalikes, eg Underground or London Transport). How that came about? Your guess is as good as mine (and don’t use that thing called the Internet to find answers).