Hi Martin – enjoyed the the video. The cowlings could have been open on that aircraft and the pilots conducting the aircraft walk around would have been none the wiser even though he put his hand on the cowling.
There are latches that could be seen to be open underneath but I gather these are often left ‘flat’ be engineers.
http://www.youtube.com/watch?v=FcScjE_QDTM – have a look at 8.30 onwards.
It would appear that this has happened before and that design changes including painting the latches in bright colours and been made.