There are just 3! = 6 ways.  In permutation word problems, when we 
see the words "a round table", we are to consider that the round table 
and chairs are placed on a large turntable such that rotating the 
people, table, and chairs around does not change the seating arrangement.  
If T is the tallest person, S is the shortest person, and A,B, and C 
are the other 3 people, then here are all 6 of the ways.


    T         T         T         T         T         T
  C   S     B   S     C   S     A   S     B   S     A   S   
   B A       C A       A B       C B       A C       B C

With a "round table", we can just consider that S and T
are always at the same fixed places so that T is to the 
immediate right of S, and permute the other 3 around them.
That's why it's 3!.

["Round table" problems are not realistic because nobody
ever puts tables, chairs, and people on large turn-tables. 
Nevertheless, that's the way to consider such problems.]

Edwin