Complex sentence: The on-screen title for Series 1 was "The Flockton Flyer" but for Series 2 it had become "Flockton Flyer" after railway enthusiasts pointed out that it is convention that locomotive names do not start with "The".
Split into simpler sentences: The on-screen title for series 1 was "The Flockton Flyer", but for series 2 it had become "Flockton Flyer". This may have been a result of complaints from some railway enthusiasts, who pointed out that it is convention that locomotive names do not start with the definite article "The".