How to Escape a Blockade

I should have learned a while ago that chairs don't work as baby gates. But our house with it's weird doorways (or lack thereof), traditional baby gates just don't work.
For the last four months, though, they've worked on the stairs. The upside down chairs trick is actually something we used with our dog when he was a puppy - we fed the cat on the stairs and put the chairs up to keep the dog away from the food. Nathan has climbed on them, but not actually shown any interest in going over them.
Until one day last week.....

This is as far as he'd gotten before... Climb up here, bounce a little, then get bored and move on.
(See why a baby gate wouldn't work? There's no wall to attach it to on the left side.)

I swear it only took him like 10 seconds to go from the floor to over the chairs.

I'm outta here!

Paul could probably rig something up with plywood and hinges, but... That would only work until he can reach over the edge and unhook it.

Really, I don't worry about him going up the steps anymore. He's a pro. It's the coming down. Especially since he thinks he can go down like a big boy now (facing forward). He's figured out how to take one step or two holding on to the wall, so he thinks he can do all of them that way. He can't.
Any experienced Mommy advice or tips?