Here is an interesting clip I found from a 1956 BBC Panorama programme which includes a depiction of BBC colour television tests from Studio A at Alexandria Palace. Note the RCA TK41.
"Panorama", the longest running current affairs programme on television, is still running on BBC1 in the UK. Richard Dimbleby, the host, describes behind the scenes at BBC television. The colour tests in 1956 followed the 405 line NTSC standard: the UK eventually adopted 625 line PAL in 1967.
https://www.youtube.com/watch?v=2G36AaMDFdM