While POKEing around inside my Spectrum, I found a location that enables a line to be scrolled over and over again on the same line:

10 FOR A=0 TO 255
20 POKE 23606,A
30 PRINT AT 10,0;"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
40 NEXT A
50 GOTO 10

Pritesh Parmar
Leicester