I'm still looking for more info on the Czech architect Hans J. Hajek 海傑克, and thus far we know:
He practiced in Shanghai from the mid-1930s onward, starting at the Universal Building & Engineering Co, and then branching out on his own.
He was named among the most prominent Central European architects in Shanghai, alongside
Laszlo Hudec and
C. H. Gonda, and might have also been a POW from the First World War in Russia.
Besides building design he also did stage sets.
His office was always located in the Associate Mission Building, 169 Yuen Ming Yuen Road.
There was a Mrs. Hajek.
Some secondary sources call him a Hungarian.
Hajek taught western architectural history at the Engineering School of St. John's University in the 1940s and 1950s. Among this stidents was the eminent architecture theorist Luo Xiaowei 罗小未 (graduate of 1948), who in her turn taught Zheng Shiling 郑时龄; both are authors of numerous books on Shanghai's historic architecture.
Hajek was still lingering in Shanghai as late as 1957...
Update from November 2021: a book by Hans J. Hajek, published in 1950. Below is an unstructured selection of Hajek’s architectural designs found in the local press.
Proposed Pere Robert Apartments, 1934:
Proposed office building for Whangpoo Road, 1934:
Plan for the "Central Building" on Nanking Road, 1935:
Proposed design of the Racecourse Apartments, end of 1935:
These proposals were also published in 1935:
(note the different Chinese spelling of his name, 海其渴)
He got a commission to design a cluster of villas on Columbia Road, west of the French Concession, at the end of 1935:
This villa on Hongqiao Road is also his creation of 1935:
Here is a letter sent to Sweden in 1957, from "海傑克 Professor Architect Dipl. Eng. Hans J. Hajek, B.A., M.B., C.E., M.A.A.S., 169 Yuen Ming Yuen Road, Shanghai, China":
Image: ebay NETA - Nobody Ever Talks About - a column on obscure architects of Shanghai.