Documents that the case worker requested:
Completed SET(O) form + photos
Current employer Letter
Three months salary slips
Three month bank statements (either saving or current account just to show economic activity)
Five years P60
Proof of business travel letters and annual leave entitlement. I guess this was required because I had around 290 days out of UK of which there were three business trips the longest of which was exactly 89 days

Co-habitation documents and marriage certificate were not asked for. However, my marriage certificate was mistakenly embedded along with the bank statements so he retained a copy just for record.
All original employer letters were retained by the case worker. Otherwise, only photocopies of the other documents.
This forum has been very useful ever since my first HSMP application way back in 2006 and then the Tier 1 FLR and now ILR. I appreciate the contribution from all members and I wish everyone good luck for their application in future. Thanks.