Joseph Mifsud, the Maltese academic suspected of being a link between the Trump campaign and Russian officials, was once a regular on the foreign policy circuit, attending conferences the world over.

Now, after being identified as a key figure in the US special counsel investigation into Russian influence over the 2016 US presidential election, Mifsud has gone to ground.

Last Thursday he disappeared from the private university in Rome where he teaches. Repeated attempts to reach him since have been unsuccessful, though he appears to have read some messages from CNN.