Tattersall took victory in the CCI short-format four star competition on Quicklook V on Saturday evening as the top three after dressage all went clear and inside the time over Ian Stark's cross country test.
That meant Laura Collett had to settle for second on Dacapo with Emily King third on Brookleigh with Northallerton Olympian Wilson a fine fourth on the promising JL Dublin as Britain were responsible for the first eight places.
The class featured a dozen riders from Yorkshire and aside from Olympian Wilson, Bramham debutante Richardson finished the highest-placed White Rose rider in the class on Caraghs Buffet in 22nd.
The pairing produced a fine clear cross country round inside the time to finish on a score of 37.2 after just 2.4 time penalties over the morning's show jumping.
Morgan Kent, better recognised as a show jumper, also went clear over cross country on Felda with just 2.8 time penalties to finish just behind Richardson on 40.5 in 24th after, unsurprisingly, a clear show jumping round.
Katie Magee capped an excellent day as Enceladus also went clear over cross country with just 4.4 time penalties to finish on 43.4 and 30th after 1.6 time penalties over show jumping.
Sophie Platt was one of only a handful of early riders to go clear cross country inside the time on Be Be III who finished in 35th on 48.6 with only 1.2 show jumping time penalties.
Platt also partnered Caesar II who was retired over cross country.
Charlotte Brear was another Yorkshire rider to go clear over cross country on Manor Missile, finishing in 42nd on 55.2 with 7.6 cross country time penalties following 0.4 show jumping time penalties.
Phil Brown was another to excel over cross country - clear and with only 7.6 time penalties to finish 46th on Harry Robinson on 62.5 after 5.2 penalties over show jumping.
Harrogate's Hazel Towers also completed another Bramham with Simply Clover 50th on 64.8 after 20 jumping penalties and 3.6 time penalties over cross country following a show jumping clear inside the time.
James Rushbrooke was next in 52nd on Zelandnew BK after 20 jumping penalties and 11.2 time penalties over cross country following 1.6 penalties over show jumping.
Then came Christopher Whittle in 54th on Skip Mill following a clear cross country round with just 4.4 time penalties after 18.8 penalties over show jumping.
Chloe Bell also completed, finishing 56th on Javas Spice after 20 jumping penalties and 6.4 time penalties over cross country following 4 penalties over show jumping.
Bedale's Sara Bowe had been well placed on Kilcoltrim Mermist but eventually retired after a couple of run outs over cross country.
The flagship long-format competition finishes on Sunday with Kitty King leading the way on Vendredi Biats but only 0.1 penalty point ahead of Tattersall on Jalapeno III.
Zara Tindall has rocketed from 15th after dressage to sixth on Class Affair while Magee is the highest-placed Yorkshire rider and even above Wilson.
Magee and Dollarney went clear inside the time over cross country to shoot up from 52nd after dressage to 15th approaching the show jumping finale.
Twenty jumping penalties plus 2.4 time penalties over cross country has left Wilson and Yacabo BK 25th on 53.7.
James Sommerville withdrew Altaskin Jack before show jumping with Storm Straker doing the same with Well Designed in the under-25s class which also finishes on Sunday.
That class is led by Britain's Yasmin Ingham on Sandman 7, ahead of fellow Brit Will Rawlin on V.I.P Vinnie.