That reminds me of fun I had on the M5 in Worcestershire in the early/mid 1970s with my white 1800. The police used white Landcrabs to patrol the M5 and as I drove people ahead would slow down thinking they were being followed. The fact that my car was a Mk1 and the police used Mk11 models didn't seem to make any difference.
I think the most majestic police cars of my youth were the Farina styled Wolseley 6/110 and Austin Westminster 6/110. They seemed to have a presence that the more exotic Jags never quite achieved.