Humanist 521 is a Bitstream digitized version of Gill Sans typeface. The font was designed by Eric Gill and released by Monotype circa 1928-1930. Gill's design is based on the typeface of Edward Johnston, the innovative British letterer and teacher, designed in 1916 for the signage of the London Underground.
However, it has more classical proportions close to those of old style serifs, and thus is more suitable for text setting. With distinct roots in handwritten scripts, Gill's typeface is classified as a humanist sans serif and is very legible and readable in text and display work. Having been released more than 80 years ago, it's still very popular and in fact is an icon of British typographic style.
The Cyrillic version of Ultra Bold weight was designed by Tagir Safaev in 1997. Six text styles and Extra Bold style in Cyrillic were designed later by Vladimir Yefimov and Isabella Chaeva. The Cyrillic version, in addition to the original Bitsteam implementation of Humanist 521, has an alternative numeral 1 with the traditional shape and a set of old-style figures. Rereleased by ParaType in 2013.