The first occurence of the Which Broadband Checker speed test in the Wayback Machine is June 2017.
This speed test is categorised as Miscellaneous because the results are lower as expected.
In addition, the speed test takes a relatively long time to complete. Hence this test is not recommended.
However, the Which Broadband Checker speed test has a nice combination of progress indicators. The overall progress indicator is in line with the progress indicators per test.
In the speed test overview you find all findings regarding the Which Broadband Checker speed test.