My instant scepticism about IG has now changed to great enthusiasm, if they continue to grow.
The political climate is totally different now than the last time a new centrist party was attempted.
We now have public disenchantment with BOTH the main parties, so the number of people potentally prepared to vote for them is greater (than in the 1980s).
At the referendum 185 Tories and 218 Labour MPs identified themselves as remainers, so as Brexit gets closer, defections to IG could spiral.
If they reach 50-60, voters might see them as the party who could go into coaltion with which ever extremist party wins the election, with a view to halting their more dangerous polucies.