Luke Clennell, driven mad by artistic logistics.

You are a painter in 1814, and you have just received the commission of a lifetime: to paint a huge canvas commemorating the Banquet for the Allied Sovereigns for the Earl of Bridgewater. Do you live happily ever after? Wikipedia tells us how the commission affected the engraver and painter Luke Clennell:

In 1814 he received from the Earl of Bridgewater a commission for a large commemorative picture, Banquet for the Allied Sovereigns, at the Guildhall, London. He experienced great difficulty in getting the more than 400 distinguished guests to sit for their portraits, suffered a mental breakdown, and spent some time in a mental asylum in Salisbury.

The next time you hear of the G-20 getting together, take a little time from grinding your teeth or cursing under your breath, and spare a thought for the photographer who has to take the commemorative group photo.