Model Sequence has no display nodes

Operating system: Linux Ubuntu 18.10
Slicer version: 4.10.1

I have created a Sequence from a number of vtkUnstructuredGrid models and get the below error when I try to play in in Sequence Browser:
virtual QColor qSlicerSubjectHierarchyModelsPlugin::getDisplayColor(vtkIdType, QMap<int, QVariant>&) const : No display node for model

The models can be seen in the 3D viewer when viewed as a model although I can’t get a slice view either.
I’m sure this is something trivial that I have misunderstood.
Thanks in advance

How did you create the models?
Did you create display nodes for the models as well?
Did you put the display nodes in a sequence or just created a single display node and associated with the model sequence’s proxy node?

The models are a series of .vtu files. one for each time increment. They contain point data connected by cells and some scalars.
Looking in the Data Module each ModelNode has a hidden associated DisplayNode. These are not something I actively created beyond importing the .vtu files. Screenshot%20from%202019-03-11%2013-23-37
When creating the sequence the only option for importable nodes are the ModelNodes.
How would I go about creating a DisplayNode?