They are the guys who put the fat into 'Fat Alberts', the madcap RAF flight sergeants Spud and Daz who spend their days sorting the loading of Wiltshire's famous Hercules aircraft.

But now Spud and Daz – or Flt Sgt Simpson and Flt Sgt Addison, to give them their proper titles – have completed the kind of mission only the foolhardy, brave or downright bonkers would attempt.

To raise money for the RAF Association charity, Spud and Daz christened themselves the "Two Fat Loadies" and set off from John O'Groats to Lands End.

But the iconic trip from the tip of Scotland to the cliffs of Cornwall would be too easy to accomplish by car in the week they were given off by bosses at RAF Lyneham.

So, en route the pair vowed to visit every single RAF base, known as air stations in the service, on mainland Britain.

Then they realised there were no fewer than 42 stations to visit, from Norfolk to north Wales and from Surrey to Aberdeenshire.

They had to cross and re-cross 56 counties, clocking up 386 miles a day.

And in case their mates back at RAF Lyneham in Wiltshire didn't believe they'd managed such a Herculean feat, the pair made sure they got pictures of themselves at all the station signs as proof of their visit.

Every RAF station eagerly anticipated their visit as they went through Scotland, northern England, Wales, the Midlands, the south east and finally into the West Country.

"We were pleasantly surprised at the amount of support we received from the stations on our trip," said FS Simpson.

"We would like to thank all the stations for their support – especially RAF Valley, who sent their RAF Association Liaison Officer to meet us.

"Thanks must also go to Marshall Aerospace for the loan of the Land Rover and the graphics," he added.

Spud and Daz are now back at RAF Lyneham, and raised more than £1,700.

"We have seen areas of the country that neither of us have visited before. It was an excellent trip and all for such a worthwhile cause," said FS Simpson

The money will help the RAFA provide welfare, help and support for any members of the RAF – past and present – and their families.

The Two Fat Loadies are planning a new expedition.