By Nigel Wynn
Mads Pedersen (Trek-Segafredo) claimed second spot after doggedly surviving from an earlier escape group. Last year's champion Philippe Gilbert (Quick-Step Floors) came home for third place to complete the podium.
Terpstra's victory after a 45km solo move means that he becomes the first Dutchman to win the Tour of Flanders for 32 years.
Having also won Paris-Roubaix in 2014 and E3 Harelbeke earlier this month, the win establishes the 33-year-old as one of the foremost Classics riders of the current generation.
How it happened
The 2018 Tour of Flanders started in Antwerp under dark skies, but despite the wet roads there was a very fast start. So fast, that mp escape group was able to form for the first 70km of the race, despite a host of riders and small groups attempting to break free.
Sep Vanmarcke (EF Education First) was one of several riders to get caught out by minor crashes caused by the slick surface and early-race nerves in the opening 50km. After enduring several bike and wheel changes, he somehow managed to stay with the bunch.
After 70km a group was finally allowed to break away from the peloton. Pascal Eenkhoorn (LottoNL-Jumbo) initiated the moves and was joined by Floris Gerts (Roompot-Nederlanse Loterij), Pim Ligthart (Roompot-Nederlanse Loterij), Ivan Garcia Cortina (Bahrain-Merida), Tom Devriendt (Wanty-Groupe Gobert), Marco Haller (Katusha-Alpecin), Ryan Gibbons (Dimension Data), Filippo Ganna (UAE Team Emirates), Michael Goolaerts (Verandas Willems-Crelan), Dimitri Peyskens (WB Veranclassic Aqua Protect) and Jimmy Turgis (Cofidis) to form a 11-rider unit.
The 11 riders quickly built up a lead of a few minutes as the speed of the peloton noticeably eased off.
Prior to the first cobbled sector of Lippenhovestraat after 87km, it was Quick-Step Floors and Team Sky taking control at the front of the peloton.
Hitting the Oude Kwaremont for the first time after 121km and with 146km to go, there were the first signs of a sort-out of both the break and peloton as the riders navigated the rough cobbled hill between huge crowds.
Watch: Tour of Flanders 2018 highlights
On the short Wolvenberg, the break was enjoying a lead of five minutes over the chasing bunch – but that would soon start to be chipped away over the following cobbles and climbs.
A crash in the peloton disrupted the race with 99km to go, with several riders falling heavily on the road and into the roadside ditches. Belgian champion Oliver Naesen (Ag2r La Mondiale) was one of those caught out, but re-mounted quickly and later re-joined the peloton. Alexey Lutsenko (Astana) did not have such good luck, and abandoned the race.
The break really started to fall apart on the Muur van Geraardsbergen just inside the final 97km, with Garcia Cortina the first to the top.
The climb also strung out the peloton, with a large and dangerous group gaining a gap over the following riders. In there were Sagan, Vanmarcke, Van Avermaet, Gilbert and Kwiatkowski.
That chase group made quick headway into closing down the gap to the break shortly after the Kanarieberg with 71km to go. Sensing an imminent catch, Devriendt and Garcia Cortina left their other breakaway companions behind.
At this stage, the skies had brightened and the roads had rapidly started to dry out and the peloton had regrouped.
With 60km to go, Devriendt and Garcia Cortina had around one minute and 20 seconds on the peloton, which had a variety of teams with riders near the front, notably Mitchelton-Scott, EF Education First and FDJ.
Just before the second pass of the Oude Kwaremont as the road narrowed around a corner Mitchel Docker (EF Education First) tumbled into some barbed wire and had to be freed by spectators.
Onto the flashpoint climb and the regrouped peloton started to stretch into pieces once again. By the following climb of the Paterberg, the main favourites had moved right to the front, with Kwiatkowski, Sagan, Gilbert and Van Avermaet right in the thick of the action.
Despite the aggressive riding behind, Devriendt and Garcia Cortina were still out front but with a slim margin of less than 20 seconds into the final 50km. They were joined by Mads Pedersen (Trek-Segafredo), who bridged across from the chasers.
Then Sebastian Langeveld (EF Education First) and Dylan Van Baarle (Team Sky) bridged over, forming a new trio with Pedersen.
The Koppenberg, with 46km to go, broke up the peloton further but with all of the main favourites putting themselves into the front group of around 30 riders.
Van Avermaet took to the front on the Taaienberg and put in a huge effort, with only a small group of riders able to follow him. The other riders caught up after the climb, and as it turned out it would be the Olympic road race champion's only major attack of the race.
Into the final 30km and onto the Kruisberg, the 30-rider chase group containing the favourites were 35 seconds behind the escape group of Pedersen, Langeveld and Van Baarle.
After the Kruisberg, Zdenek Stybar (Quick-Step Floors) put in an attack and was followed by Sagan and Kwiatkowski. After they were caught, almost immediately Milan-San Remo winner Vincenzo Nibali (Bahrain-Merida) attacked and was followed by Terpstra. Nibali, though, faded with the effort, leaving Terpstra to forge ahead and close in on the trio up front in what would be the decisive move of the race.
Terpstra's move meant that Quick-Step's riders could ease off in the bunch, letting others do the chase work – and it was BMC and Astana who took up the reins into the final 25km.
Terpstra finally made contact with the leaders on the last pass of the Oude Kwaremont with 19km to go. He didn't hang about, moving straight to the front and leaving Langeveld and Van Baarle behind and with Pedersen fighting to stay on his wheel.
With Pedersen distanced, Terpstra then found himself in familiar territory, solo at the front of the race – just as he did to win E3 Harelbeke.
Terpstra crested the final climb of Paterberg out front, with Pedersen a handful of second behind and the chasing group led by Sagan around 30 seconds back.
Rounding the left-hand corner at the top of the Paterberg, Sagan put in a big acceleration and started to attempt to chase down Terpstra and Pedersen on his own but could not make any headway. The world champion sat up with 8.5km to go to rejoin the rest of the group.
With 7km to go, Terpstra was crouched over his bars, his cheeks specked with spittle from his effort and with 20 seconds ahead of Pedersen and 40 seconds ahead of the Sagan group. Some disarray among the organisation of the chasers played firmly to his favour.
As Terpstra rolled over the line in celebration, Pedersen was putting in a huge effort to keep the chasers at bay, and hung on for second place ahead of Gilbert. The following group containing Sagan and Van Avermaet could only look on, perhaps saving their efforts for the following weekend's Paris-Roubaix.
Team Sky suffered an ultimately disappointing race, after Kwiatkowski did not make the top 10 and Luke Rowe was disqualified for riding on a pavement behind spectators.
Earlier in the day, Dutch rider Anna van der Breggen (Boels-Dolmans) won the women's edition of the Tour of Flanders giving the Netherlands two winners on the roads of Belgium.
Tour of Flanders 2018, 267km
1. Niki Terpstra (Ned) Quick-Step Floors
2. Mads Pedersen (Den) Trek-Segaredo
3. Philippe Gilbert (Bel) Quick-Step Floors
4. Michael Valgren (Den) Astana
5. Greg Van Avermaet (Bel) BMC Racing
6. Peter Sagan (Svk) Bora-Hansgrohe
7. Jasper Stuyven (Bel) Trek-Segafredo
8. Tiesj Benoot (Bel) Lotto-Soudal
9. Wout van Aert (Bel) Verands Willems Crelan
10. Zdenek Stybar (Cze) Quick-Step Floors
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