Resolve incorrect conversion from Long-Lat to British National Grid

product affected: MapInfo Pro™

Issue

After converting a table from Longitude-Latitude to British National Grid some points do not appear where expected.

Cause

When converting a table that is in a coordinate system without a datum, such as Longitude/Latitude, to a coordinate system that does have a datum, such as Longitude/Latitude Nad83, it is possible to experience inaccuracies up to 300m.

Resolution

UPDATED: December 4, 2019
Use a coordinate system that has a datum parameter.

For example, instead of importing the data as Longitude-Latitude and then converting it to British National Grid, use Lon\Lat (WGS84) and then convert to British National Grid.