Cafodd Ymddiriedolaeth GIG Felindre ei hysbysu gyntaf gan Landauer am y digwyddiad ar 17 Ionawr 2017, a hynny drwy lythyr. Cafodd manylion llawn y digwyddiad eu darparu’n electronig i Ymddiriedolaeth GIG Felindre ar 26 Ionawr 2017. Ar ôl derbyn y manylion hyn, dechreuodd Ymddiriedolaeth GIG Felindre ar ddadansoddiad manwl i ddilysu a glanhau’r data a ddarparwyd, a oedd yn cwmpasu cyfnod o chwe blynedd. Drwy wneud hyn, daethpwyd o hyd i’r unigolion a oedd wedi cael eu heffeithio gan y digwyddiad. Roedd hwn yn gam pwysig yn y broses o ddileu cofnodion dymi, dod o hyd i gofnodion dyblyg, a dilysu’r manylion cyswllt cyfredol ar gyfer y rheini a oedd wedi’u heffeithio, ac yn bwysicach na hyn, roedd yn sicrhau na fyddai unrhyw ymgais i geisio cysylltu ag unigolion a oedd wedi marw. Wrth i’r wybodaeth ddod i’r fei, cafodd yr arweinwyr ym mhob Bwrdd Iechyd a phob grŵp nad yw’n perthyn i’r GIG, eu hysbysu gan Ymddiriedolaeth GIG Felindre. Cafodd y gwaith hwn ei wneud rhwng 22 Chwefror a 9 Mawrth 2017.
Velindre NHS Trust was  first notified about the incident by Landauer on the 17 January 2017 by letter. Full details of the incident were provided electronically to Velindre NHS Trust by Landauer on 26 January 2017. Once received, Velindre NHS Trust commenced an in-depth analysis to validate and cleanse the six years worth of data supplied, in order to identify affected individuals. This was an important step in the process to remove dummy entries, identify duplicates, establish current contact details for all those involved, and more importantly, to ensure that there was no attempt to contact individuals who had since passed away. As information became available, the leads in each of the Health Boards and non-NHS groups were informed by Velindre NHS Trust. This was carried out between 22 February and the 9 March 2017.