CONFUSION IN THE TFC PATTERN LEADS TO AN NMAC.

Narrative

I WAS TAKING INSTRUCTION FOR REFAMILIARIZATION IN A BEECH SIERRA C-24R. I FLEW L SEAT WITH AN INSTRUCTOR IN THE R SEAT. AFTER SEVERAL PRACTICE TOUCH-AND-GOES; I WAS ON L DOWNWIND FOR A FULL STOP LNDG. THE TWR INSTRUCTED ME TO FOLLOW A NAVAJO ON DOWNWIND. I ACKNOWLEDGED HAVING THE NAVAJO IN SIGHT. WHEN I WAS ON ABOUT A 2 MI FINAL FOLLOWING THE NAVAJO; A HIGH WING CESSNA (PROBABLY C-172) WHO HAD BEEN BEHIND ME ON DOWNWIND; BEGAN APCHING FROM THE L AND ABOVE; APPARENTLY ON A HIGH L BASE. I POINTED THIS OUT TO THE TWR. THE TWR TOLD THE CESSNA TO FOLLOW THE SIERRA (MY ACFT). THE CESSNA ENTERED A L TURN ONTO FINAL IN FRONT OF ME. IN HIS TURN HE ANNOUNCED HE HAD THE SIERRA IN SIGHT. BECAUSE OF HIS TURN ATTITUDE; THE CESSNA PLT COULD NOT HAVE SEEN ME. HE PROBABLY MISTOOK THE NAVAJO FOR THE SIERRA. I WAS ABOUT TO FLY DIRECTLY UNDER THE CESSNA; SO I MADE AN IMMEDIATE L TURN; ANNOUNCING THIS TO THE TWR. I THEN REJOINED THE L DOWNWIND BEHIND ANOTHER CESSNA ON DOWNWIND AND INFORMED THE TWR OF MY POS. THE CTLR WAS APPARENTLY CONFUSED BECAUSE HE AMENDED MY CLRNC TO LAND BEHIND THE FIRST CESSNA; THEN RE-AMENDED THE CLRNC TO LAND BEHIND THE SECOND CESSNA. THIS IS A GOOD EXAMPLE OF THE IMPORTANCE OF CONTINUOUS VIGILANCE IN THE TFC PATTERN; EVEN IN A TWR ENVIRONMENT.