Cummings had started the day occupying the top spot of the general classification 49 seconds ahead of Tom Dumoulin (Giant-Alpecin) and 51 seconds ahead of Rohan Dennis (BMC Racing) – both noted time triallists.
As Dennis can home with 18-09 and Dumoulin just behind with 18-11, Cummings needed to set a time of 19 minutes or quicker to retain the yellow jersey.
The Wirral man put in a strong ride, coming over the line with 18-22 to easily keep hold of his overall race lead with two stages remaining.
Tony Martin (Etixx-QuickStep) took the stage win on the short and fast 15-kilometre course, clocking 18-06. Dennis was second, Dumoulin third and Cummings fourth. Britain’s Alex Dowsett (Movistar) finished seventh.
Sir Bradley Wiggins (Team Wiggins) took to the start house on his road bike, waving to the crowds on what is touted as his final appearance in his ‘home’ tour.
Taylor Phinney (BMC Racing) had started quickly and set the fastest time at the mid-way point, but suffered a crash to scupper his chances of a high finish. To his credit, he still came home in 11th.
The 2016 Tour of Britain continues on Saturday afternoon with stage 7B in Bristol, a brisk 76.5km circuit race. It’s then on to London on Sunday for the race finale. It is likely that Cummings will now take the overall victory – barring disaster – given his 38 second GC advantage over Dumoulin and Dennis.
The Tour of Britain’s split stage on Saturday, with a time trial in the morning and circuit race in the afternoon, is something of a miniature dry-run for the World Championships in October. Many of the leading contenders in the Worlds are using the race as a warm-up and form guide.
The presence of Martin, Dumoulin and Dennis in the top order of the TT results shows that they will be the riders to watch at the Worlds in Doha, Qatar over October 9-16. Cummings has also put his name forward very convincingly to British selectors to represent GB in the Worlds TT.
Tour of Britain 2016, stage 7A: Bristol to Bristol, 15km ITT
1. Tony Martin (Ger) Etixx-QuickStep in 18-06
2. Rohan Dennis (Aus) BMC Racing at 3 secs
3. Tom Dumoulin (Ned) Giant-Alpecin at 5 secs
4. Steve Cummings (GBr) Dimension Data at 16 secs
5. Tony Gallopin (Fra) Lotto-Soudal at 25 secs
6. Gorka Izaguirre (Esp) Movistar at 25 secs
7. Alex Dowsett (GBr) Movistar at 35 secs
8. Nicolas Roche (Irl) Team Sky at 36 secs
9. Ryan Mullen (Irl) Cannondale-Drapac at 39 secs
10. Dylan Van Baarle (Ned) Cannondale-Drapac at 40 secs
11. Taylor Phinney (USA) BMC Racing at 40 secs
12. Tao Geoghegan Hart (GBr) Great Britain at 44 secs
General classification after stage 7A
1. Steve Cummings (GBr) Dimension Data
2. Tom Dumoulin (Ned) Giant-Alpecin at 38 secs
3. Rohan Dennis (Aus) BMC Racing at 38 secs
4. Tony Gallopin (Fra) Lotto-Soudal at 1-02
5. Dylan Van Baarle (Ned) Cannondale-Drapac at 1-21
6. Nicolas Roche (Irl) Team Sky at 1-26
7. Xandro Meurisse (Bel) Wany-Groupe Gobert at 1-48
8. Ben Swift (GBr) Team Sky at 1-52
9. Julien Vermote (Bel) Etixx-QuickStep at 2-08
10. Jacopo Mosca (Ita) Trek-Segafredo at 2-32