We have now received a response which is as follows:
Hi Emanuele,
My name is xxx, and I will be triaging your Support Case #0336xxxx.
If I cannot resolve your issue, I will pass your Support Case on to a dedicated analyst who will work with you to reach a resolution.
Thank you for raising this issue with us.
We have received a small number of reports from Esri UK Customers surrounding British National Grid data not being projected correctly when used in the following ways:
- BNG Data with a WGS84 Basemap in Map Viewer Classic
- BNG Data with a WGS84 Basemap in ArcGIS Field Maps
This behaviour occurred following the June release of ArcGIS Online and we have logged a high severity Bug with Esri Inc. for this to be looked into as a matter of priority.
This issue is currently being investigated by the product engineers with Esri Inc., and we will continue to provide updates as we receive them. We have attached your case to the bug, and we ask for you to escalate the severity of the Bug from within MyEsri: How To: "Escalate a Bug in My Esri "
In the meantime, the following have been identified as workarounds whilst Esri Inc. work on this issue:
- Wherever possible please utilise new Map Viewer when authoring web maps in ArcGIS Online,
- Should you require Map Viewer Classic, or ArcGIS Field Maps to carry out your workflows, this behaviour is not reproducible with BNG basemaps at this time
Please be assured that we are treating this issue as a matter of urgency, and we will keep providing you with updates as soon as we receive them.