Christopher Kempf, the statistical analyst of the PDC, looks at the bull & 25 set-up shot.

Raymond van Barneveld's signature finish is 156, a roof-raising three-dart checkout which he has completed on dozens of occasions - a greater frequency, perhaps, than any other player - including on two in 2017.

He was, however, outdone last year by world number two Peter Wright, who fired in four such checkouts, completing the three-dart combination in 11% of his attempts.

That was far from his most impressive performance in the domain of high checkouts, however while Wright may not have a signature finish of his own, he demonstrated remarkable virtuosity while attempting 116 finishes.

Of all the stage 116 checkouts recorded in the PDC in 2017, Wright was responsible for nearly a quarter.

The reason whese two players keep attempting 116 and 156 finishes is because of their affinity for the bullseye.

Their solution to the problem of rounding off the odd number one in 501 is to throw for the unique ring-shaped 25 bed and not to wait until a stray dart at treble 20 lands in the one or five beds.

Players who do this attempt to use the 25 to jump ahead to a slightly easier category of finish: 25 scored from 181 leaves 156 instead of 161, eliminating the need to use the bullseye for a checkout; 25 scored from 121 leaves 96 instead of 101, giving a player an opportunity to check out in two darts, or alternatively to attempt another dart at double; 25 scored from 101 leaves 76 instead of 81, which again yields a dart at double rather than at the bullseye.

Wright and Van Barneveld are two of the most notable exponents of using the bullseye for the purpose of setting up an easier finish, but they are by no means the most aggressive adopters of this strategy.

Since December, more than two percent of all darts thrown by Mensur Suljovic, Daryl Gurmey and Gerwyn Price were set-up darts aimed at the bullseye, yielding an overall rate higher than that of either Van Barneveld or Wright.

To some extent it has become, over the past ten years, fully incorporated into the setup calculus of most top players. But does it work?

At first glance, it may appear that attempting a bullseye outside of a checkout situation is a losing strategy.

Each individual dart at bullseye scores, on average, 27.16 points, nearly seven less than a single dart at treble 20, and comes with more than twice the risk of leaving an unwanted score via a stray dart into the single-number segments which converge at the bullseye.

21% of PDC professionals' darts at the bullseye land in these segments, while only 9% of darts at most scoring trebles miss both the treble and single of the segment in question.

A high level of accuracy around the bull is therefore needed to make this setup strategy work.

The appeal of the 25 setup shot is evident when comparing the checkout percentages of pairs of finishes implicated by the strategy.

A 161 checkout occurs rarely - fewer than 20 times over 12,000 legs played in 2017 - though it is one of the most frequently attempted of all finishes. Only 2% of these checkouts are successful.

156, on the other hand, is perhaps the easiest checkout of its kind, requiring two trebles in the same bed and a double at a similar height on the dartboard, and has a success rate more than quadruple that of the 161 finish.

When comparing all possible checkout scenarios' 2017 completion percentage with the average PDC player's propensity to hit different segments around the target at which he aims, the bull route yields about one additional checkout in four darts per 200 attempted.

This analysis would not be enough to override a player's desire to fill up an inviting treble 20 bed, but it does confirm that, all other things being equal, bullseye is (by a small margin) the mathematically correct target with a last dart in hand from 181.

BULL ROUTE: Four darts from 181

Segment Probability Resulting Finish % Checkout % In Four Darts 25 (56%) 156 (8.5%) 4.76% Bullseye (23%) 131 (4%) 0.92% 11, 14, 17, 20 (4.2%) 170, 167, 164, 161 (2.5%) 0.11% 1-10, 12-13, 15-16, 18-19 (16.8%) No Finish (0%) 0.00% Total 5.79%

TREBLE 20 ROUTE: Four darts from 181

Segment Probability Resulting Finish % Checkout % In Four Darts Treble 20 (38%) 121 Finish (11%) 4.18% Single 20 (53%) 161 Finish (2%) 1.06% 1, T1, 5, T5 (9%) No Finish (0%) 0.00% Total 5.24%

However, this advantage evaporates when considering a scenario requiring a checkout in four darts from 141, or from 101.

In these situations, the advantage gained from leaving 116 or 76 via the 25 segment versus the 121 or 81 success rate is far less.

Hitting a 116 checkout is only 1.78 times more likely than a 121; a 76 checkout is only 1.27 times more likely than an 81.

Here the higher stray dart percentage around the bullseye also becomes a more important factor in depressing the success rate of bull setups:

BULL ROUTE: Four darts from 141

Segment Probability Resulting Finish Checkout % In Four Darts 25 (56%) 116 Finish (19%) 10/64% Bullseye (23%) 91 Finish (26%) 5.98% 1-20 (21%) Various Finishes (Ave 7.5%) 1.58% Total 18.20%

TREBLE 20 ROUTE: Four darts from 141

Segment Probability Resulting Finish Checkout % In Four Darts Treble 20 (38%) 81 finish (37%) 14.06% Single 20 (53%) 121 finish (11%) 5.83% 1, T1, 5, T5 (9%) 140, 138, 136, 126 (Ave 6%) 0.54% Total 20.43%

Here, a dart at treble 20 rather than at bullseye gives a player an extra checkout per 50 attempts with four darts from 141.

Factors such as blocked-ness of the treble bed and the opponent's score make for stronger motive forces behind a player's decision to attempt a bullseye setup shot than the mathematical analysis of probabilities demonstrated above.

With more extensive data collection from more players, it will soon be possible to calculate this sort of strategical assay of an individual player's game.

That may eventually vindicate Peter Wright's particular penchant for the 116 checkout.

But it seems clear that Raymond van Barneveld not only entices the audience, but also exploits a statistical shortcut in the game of 501 with every signature 156 "Barney finish".