The brothers Iron 'Arry and Iron Bert are diesel engines who work at the scrapyards and smelters of Sodor Ironworks. Their bodies are dark green with yellow hazard stripes.
They feel superior to steam engines, and working at the scrap yards, they enjoy the chance to break up engines, or at least make their lives more difficult. They've earned a reputation on Sodor as "The Grim Messengers of Doom." Despite their prejudices, the diesels have co-operated with steam engines on occasion, and when they're in trouble, steam engines often come to the rescue.
'Arry & Bert are British Rail Class 08 diesel-electric shunters.