My client decided to inform DWP in writing that he did not want to continue with his ESA appeal in May 2010 and has now sought our advice - we feel he may have a fairly strong case to challenge original ESA decision - can anyone advise me on requesting that DWP overturn his request to end his appeal?

I haven't actually actually dealt with this scenario before.......we usually manage to advise clients not to withdraw their appeal before they send the letter back to DWP!?!

All help appreciated - and apologies if this seems like a daft question...........it's been a very long day............

The only way I have had an appeal reinstated following the withdrawal of the appeal at the client behest is to ask for a "late appeal", ie apply to extend the time limit to appeal with grounds that your client was either misinformed or unaware of all the issues surrounding the complex processes of appealing.
However, the original decision must have been made within the last 12 months

You can request reinstatment of an appeal within one month of the Tribunal Service receiving the request to withdraw (see CPAG p 1143). The letter from TS confirming withdrawal should state this. As you say the appeal was withdrawn in May, perhaps your client is still within this time limit?