True to their word Eurotunnel replied to Ian's complaint that he made whilst we were waiting for our delayed departure. Here is an abbreviated version of the reply.
Thank you for contacting us following your recent journey with Eurotunnel.
We regret that you were unable to board your reserved shuttle as planned on 21 December and we would like to provide you with some explanation : (In summary we are still repairing the tunnel after the fire and sometimes things run over a bit or the cars take up more room on the shuttle that we thought they would and so we run out of space).
As a gesture of goodwill, we would like to offer you a £30 supplement for travel at "high peak" time on a next Frequent Traveller ticket. This offer is valid for six months with effect from the date of this message.
Thank you for your patience and your understanding.
It would have much cheaper for them to have given us free coffee and we would have been happy with that!