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How fast could Colossus I process characters?

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The Colossus computer at Bletchley Park, Buckinghamshire, England, c. 1943. — Colossus Funding for this code-breaking machine came from the Ultra project.

Colossus I was capable of processing data at a speed of 5,000 characters per second. This performance was a significant improvement over its predecessor, the "Heath Robinson" machine, which could only read paper tapes at a rate of 1,000 to 2,000 characters per second.1

By utilizing this electronic speed, Colossus I enabled code breakers at Bletchley Park to analyze over 100 messages per week. Later versions of the machine, known as the Mark II Colossi, further increased this capability to 25,000 characters per second through the use of parallel processing.1