The ultimate hokey-cokey cabinet post?

Most people get just the once chance at any one job in government. It's very unusual (Mandelson with the DTI aside, and Mandelson seems to be an exception to most political rules) for someone to go back to a job a second time.

At Cabinet level, Mandelson has done it, Roy Jenkins with the Home Office has, and I think that's it, post war. There's been the odd time of someone going to back to a job they'd previously done when their party had been out of office but picking up where you left off but for the intervention of the electorate is slightly different.

So why has the SoS for Wales post (perhaps the post with the least responsibility in all government) had this retread effect twice, with both Murphy and Hain?

Secretary of State for Wales
July 2009: Paul Murphy
October 2002: Peter Hain
January 2008: Paul Murphy
June 2009: Peter Hain

Last time Hain did this job, he doubled it with the DWP job (replaced by Mr Purnell) but suddenly, in the intervening 18 months the job must have grown in importance and Hain no longer doubles-up.

Presumably, this reshuffle has been made for the same reason that Jim Murphy is in Scotland - to run campaigns for the Labour party. By any stretch of the imagination Hain is a better campaigner than (Paul) Murphy (Paul Murphy wouldn't recognise a campaign if it introduced itself) and Wales has the 2nd highest proportion of Labour seats of any UK region (and it's a bit tricky to justify a full-time Secretary of State for the North East).