The Commonwealth 100m champion has repeatedly set British records for 50m and 100m backstroke, long and short-course, since claiming Gary Abrahams' 100m long-course mark - which had stood for 10 years - in 1990.
However, Harris's title could be captured by the 19-year-old Neil Willey from Hertfordshire who, despite being the youngest swimmer in the field, won the 100m backstroke silver medal at the World Short-Course Championships in Rio de Janeiro a fortnight ago.
Willey's time of 53.23sect was only 0.08sec outside the British record, and Harris's chances of fending off the young swimmer's challenge - starting in the heats of the 50m backstroke today - cannot have been helped by the fact he is now without either a club or a coach.
Harris quit the Borough of Waltham Forest club in the summer, upset by their decision not to award a new contract to the club coach, Paul Bance.
Bance is now coaching in Wales, but Harris did not want to follow him from his home in east London, and he is now training at a local pool helped only by his father, Raymond, who said: "I take down his times, but really Martin is coaching himself.
"It's not an ideal situation as everyone needs a proper coach's support, but Martin is a good self-motivator."
The Winter Challenge, incorporating the Amateur Swimming Association's National Winter Championships, effectively marks the start of the countdown to the Olympic Games in Atlanta for top competitors such as Nick Gillingham.
The double Olympic medallist believes he can start his preparations in style by reclaiming the world short-course 200m breaststroke record which he held for two-and-half-years before the Australian Phil Rogers set the existing mark of two minutes 07.80sec in August 1993.
Gillingham said: "In my opinion, Sheffield is the fastest pool in the world, and having home support behind me may just give me the extra one per cent I need to beat the record."Reuse content