Merc handlebar adjustment
 

I have recently purchased two secondhand Merc three speed folding bikes. I have been looking at Bromptons for a long time, but the prices secondhand are still very high so opted for the cheaper bike. On one of the Mercs the bars are out of alignment with the front wheel, no problem I thought, undo the allen bolt and adjust as per an old fashioned road bike stem.
However I cannot move this allen bolt, I have successfully twisted an allen key, but the bolt did not move. I do not have a manual or any information for the bike.

Can somebody tell me where I am going wrong?

Maybe your allen key was of poor quality? I did this with my Merc last week. The bolt is just tight.

Forgot to mention that I had a 19mm ring spanner on the end of the allen key for extra leverage, I think I will try the other bike to see if that one will undo.