Exiting an 80k zone from he hutt towards Wellington,inside lane. I see a marked car with radar. Flashing lights come on & a mufti car start pusuing in the fast lane. As we hit the motorway,hes in the outside lane but hes not pulling anyone over,just sitting in the outside lane,lights flashing,doing 70-80kph holding both lanes back.his goes on for about 4k,he then pulls into slow lane,turns off lights & carrys on doing 80.I then jump into outside lane & overtake him doing 100. What the **** was that all about?