These were much less expensive than transistors, yet enough of them were used in the design that replacing just the diodes would still result in a significant simplification and improvement in reliability.
At that time computers were used almost always in the sciences, and they decided to add a floating-point unit to greatly improve performance in this role.
Like the Mark I, Meg was based on a 10-bit "short word", combining two to form a 20-bit address and four to make a 40-bit integer.
[1] Ferranti, which had built the Mark I for the university, continued development of the prototype Meg to produce the Mercury.
Although slower to access, at about 10 μs for a 10-bit short word, the system required virtually no maintenance, considerably more important for commercial users.
[2] Manchester University received one in February 1958, leasing half the time to commercial users via Ferranti's business unit.
[5] The machine could run Mercury Autocode, a simplified coding system of the type later described as a high-level programming language.