The 26-year-old from Walsall, who won the 200m breaststroke bronze medal at the Barcelona Olympics last year, arrived at the Mycil ASA National Championships and European trials with an undistinguished record this year.
However, Gillingham won his heat in the morning in 1min 2.19sec, just inside the previous world best this year, set in April by Seth Van Neerden, of the United States, and improved upon that by winning the final in the evening with a time of 1:2.16.
Gillingham had already been selected for the European Championships at 200m, which he will be attempting to win for a record third time, but he is eager to prove that he can also beat Europe's best over 100m.
Kathy Osher, of Barnet Copthall, lowered her own British record by 0.06sec in winning the 50m backstroke in 30.00.
MYCIL ASA NATIONAL CHAMPIONSHIPS Finals (Sheffield): MEN: 50m backstroke: 1 M Harris (Borough of Waltham Forest) 26.65sec; 2 N Willey (Barnet Copthall) 26.99; 3 J Fleet (Borough of Waltham Forest) 27.99. 100m freestyle: 1 M Fibbens (Barnet Copthall) 50.55; 2 A Rapley (City of Sheffield) 51.05; 3 M Carl (Redbridge Borough) 51.55. 100m breaststroke: 1 N Gillingham (City of Birmingham) 1min 02.16sec; 2 R Maden (City of Leeds) 1:03.13; 3 I Swift (Rotherham Metro) 1:04.31. 200m individual medley: 1 F Walker (Warrender) 2:03.77; 2 G Robins (Portsmouth Northsea) 2:06.84; 3 D Warren (City of Leeds) 2:06.90. 4 x 100m medley: 1 City of Birmingham 3:50.79, 2 City of Leeds 3:53.15, 3 City of Sheffield 3:53.31. WOMEN: 50m backstroke: 1 K Osher (Barnet Copthall) 30.00 (British record); 2 H Slatter (Warrington Warriors) 30.75; 3 A Bennett (Nova Centurion) 31.15. 100m breaststroke: 1 J King (Tigersharks) 1:11.55; 2 M Hardiman (City of Birmingham) 1:11.85; 3 Z Baker (City of Sheffield) 1:12.82. 200m freestyle: 1 K Pickering (Ipswich) 2:02.59; 2 C Huddart (City of Leeds) 2:04.12; 3 S Hardcastle (Borough of Southend) 2:04.27. 200m individual medley: 1 L Findlay (Kelly College) 2:19.03; 2 S Rolph (City of Newcastle) 2:20.63; 3 H Slatter (Warrington Warriors) 2:20.65. 4 x 100m freestyle: 1 Nova Centurion 4:00.88; 2 City of Cardiff 4:02.23; 3 City of Leeds 4:04.91.Reuse content