It is plausible (if not yet publicly proved) that the theft of the Auschwitz sign was committed to 'fund Swedish neo-Nazi terrorist attacks'; and it appears that the funder was a British neo-Nazi collector.
Previously, the most specific claim about the terrorism-funding private antiquities collector was Marcus Oscarsson and Jenny Booth's claim that the 'collector [was] in England, France or the United States'.
Now, Michael Woodhead has reported that 'he' was a 'British Nazi sympathiser' and 'collector of Nazi memorabilia', who wanted Auschwitz-Birkenau death camp's "Arbeit Macht Frei (Work Makes You Free)" sign as a 'trophy'.
According to Woodhead, 'well-placed underworld informants' dismissed the Polish thieves as 'just bit-part players'; and police have identified '"a European mastermind" [who] could be arrested'.
Oscarsson, M and Booth, J. 2009: "Auschwitz sign 'stolen to fund Swedish terror attacks'". The Times, 24th December. Available at: http://www.timesonline.co.uk/tol/news/world/europe/article6967449.ece
Woodhead, M. 2010: "Auschwitz sign was stolen for wealthy British Nazi". The Sunday Mirror, 3rd January. Available at: http://www.mirror.co.uk/news/top-stories/2010/01/03/auschwitz-sign-was-stolen-for-wealthy-british-nazi-115875-21937555/