AN SMA CUTS INTO PATTERN IN FRONT OF TWIN AT TWR CTLED ARPT.

Narrative

I WAS INSTRUCTING IN SMA TWIN Z IN L CLOSED TFC AT GROTON ARPT (GON) DURING THE OP OF THE CTL TWR AND UNDER ATC CTL. I WAS SEQUENCED BEHIND AN SMA X WHICH I HAD IN SIGHT WHILE ON 2 MI R BASE. UPON CALLING THE SMA X IN SIGHT; I WAS 'CLRED TO LAND; #2' ON RWY 23. MEANWHILE; AN ACFT SMA Y HAD CALLED THE TWR; RPTING '5 E FOR THE R BASE TO RWY 23.' WHEN TOLD BY THE TWR THAT THIS WOULD SET HIM UP FOR A L BASE; THE PLT DID NOT RESPOND. ABOUT TO TURN FINAL; I SAW THIS UNSEQUENCED TFC CUTTING IN FRONT OF ME ON FINAL. TWR ASKED HIM WHAT HE WAS DOING. HE RESPONDED THAT HE WAS AHEAD OF ME AND WAS LNDG. I SAID OVER THE FREQ 'TOO LATE; I'LL BE #2.' THE OTHER PLT REITERATED OVER THE FREQ THAT HE WAS WELL IN FRONT OF ME. I INTERJECTED ON FREQ THAT HE WAS FOLLOWING THE WRONG TFC; BUT HE WAS CLRED TO LAND BY TWR; AND I WAS SEQUENCED #2. UPON SEEKING OUT THE PLT ON THE GND; HE SHOWED NO REMORSE OR AWARENESS OF THE DANGER OF HIS ACTION. HE BLAMED THE INCIDENT ON THE TWR AND ALSO STATED THAT THERE HAD BEEN 'PLENTY OF ROOM' BTWN US. IN MY ESTIMATION THERE WAS PERHAPS 1000 FT VERT SEPARATION AND '0' FT HORIZ.