The Crown displays weren't originally designed for ATC use, they were adapted from a design supplied to the RN for use with shipboard air defence radars. They worked OK in ATC though and had a built in qwerty keyboard and rolling ball and the picture consisted of 'proper' blips (albeit processed then put back in 'raw radar' form) rather than a plot extracted symbol as with TFT displays.
In the 6 years I used TFT displays at Farnborough (Nov 2002 - to Nov 2008) I never felt as 'secure' with processed radar as when looking at proper 'blips' as you were never sure what the processor had processed out that you might need to see (eg slow moving aircraft like microlights and PPGs) due to its reliance on using a 'threshold speed' of as much as 50kts as part of the processing.