The Dimension Data rider enjoyed a good lead-out effort from Mark Renshaw, but as Viviani accelerated hard on the left-hand side of the road, Boasson Hagen moved to the left to shut the door on the Italian.
Viviani gesticulated as he crossed the line as Boasson Hagen celebrated in front of him, but was later awarded the stage victory as Boasson Hagen was relegated to last place in the lead group, 109th.
That result was also enough to move Viviani into the race lead as erstwhile green jersey Caleb Ewan (Orica-Scott) finished out of the time bonuses in fourth.
How it happened
As was the case on the opening stage, stage two of the 2017 Tour of Britain saw a decent-sized break with seven riders going up the road and four domestic teams represented. In the move were Rory Townsend (Bike Channel-Canyon), Graham Briggs (JLT Condor), Matthew Holmes (Madison Genesis), Lukasz Owsian (CCC Sprandi Polkowice), Kamil Gradek (One Pro Cycling), Jacob Scott (An Post Chain Reaction), and Silvan Dillier (BMC Racing).
Those seven riders quickly established a three minute advantage over the main peloton, which went out to five minutes after three KOM points in relatively quick succession, Scott winning the first being being pushed into second place by Briggs at the subsequent two KOMs.
However, with most of the climbing out of the way for the day, the sprinters' teams were able to take control on the front of the bunch, with Orica-Scott, Team Sky, and Dimension Data trimming the gap back to below three minutes with more than 100km still remaining.
The break was kept under close control through the final 100km, falling below 30 seconds with 20km remaining which prompted Holmes to attack from the break. While the rest of the move was quickly caught, Holmes put up more of a fight, lasting another eight kilometres and sweeping up maximum points at the final intermediate sprint in the process.
The race all back together, the stage was set for another big bunch sprint in Blyth, Katusha-Alpecin, Orica-Scott, and Dimension Data controlling the front of the bunch. However the pace wasn't high enough to deter attacks, with Philippe Gilbert (Quick-Step Floors) going for an audacious move with eight kilometres to go.
Gilbert's move was bold, holding off the pack for three kilometres, before Team Sky pulled him back with Geraint Thomas working hard on the front.
>>> Tour of Britain 2017 route: stage-by-stage details and where to watch
With only six riders in each team it was hard for a single team to stay in control, with Orica-Scott and Katusha-Alpecin also fighting for control.
However, it was Dimension Data who led in to the final kilometre, Boasson Hagen being put in a perfect position with 300m to go, but being put under pressure by Viviani who accelerated hard on the left-hand side of the road.
For a few moments the two riders were neck-and-neck, before Boasson Hagen eased in front and moved over to the left of the road, shutting the door on Viviani who raised his hand in protest while Boasson Hagen celebrated the win.
However, after a few minutes delay, the commissaires decided to relegate Boasson Hagen, handing Viviani victory and also the overall race lead as Ewan finished in fourth.
Tour of Britain 2017, stage two: Kielder Water and Forest Park to Blyth (211.7km)
1. Elia Viviani (Ita) Team Sky, in 5-16-31
2. Dylan Groenewegen (Ned) LottoNL-Jumbo
3. Fernando Gaviria (Col) Quick-Step Floors
4. Caleb Ewan (Aus) Orica-Scott
5. Alexander Kristoff (Nor) Katusha-Alpecin
6. Zdenek Stybar (Cze) Quick-Step Floors
7. Floris Gerts (Ned) BMC Racing
8. Roger Kluge (Ger) Orica-Scott
9. Marcel Sieberg (Ger) Lotto Soudal, all same time
109. Edvald Boasson Hagen (Nor) Dimension Data, same time (relegated)
General classification after stage two
1. Elia Viviani (Ita) Team Sky, in 9-50-35
2. Caleb Ewan (Aus) Orica-Scott, at 4 secs
3. Edvald Boasson Hagen (Nor) Dimension Data, at 7 secs
4. Karol Domagalski (Pol) One Pro Cycling, at 9 secs
5. Silvan Dillier (Sui) BMC Racing, at 9 secs
6. Kamil Gradek (Pol) One Pro Cycling, at same time
7. Fernando Gaviria (Col) Quick-Step Floors, at 10 secs
8. Lars Boom (Ned) LottoNL-Jumbo, at 12 secs
9. Alexander Kristoff (Nor) Katusha-Alpecin, at 14 secs
10. Zdenek Stybar (Cze) Quick-Step Floors, at same time
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