Every Saturday evening he sends out an email to a number of party activists and staff and this week he has taken the opportunity to send a brief message expressing his gratitude to all those who have been in touch, not least because he is not presently in a position to acknowledge them all individually.
Some ConservativeHome readers will receive his email in any case, but many will not, so we have been asked to publish David's message in full so that everyone who has written to him knows how much he and the Cameron family have appreciated it.
It reads as follows:
"Sam and I have been overwhelmed by all the letters, cards, emails and flowers we have received about Ivan. Sending an email this week just gives us both a chance to say a big "thank you". It means a lot to know that others are thinking of us and him.
"We always knew Ivan wouldn't live forever, but we didn't expect to lose him so young and so suddenly. He leaves a hole in our life so big that words can't describe it. Bed time, bath time, meal time - nothing will feel the same again.
"We console ourselves knowing that he won't suffer anymore, that his end was quick, and that he is in a better place. But we all just miss him so desperately.
"When we were first told the extent of Ivan's disability I thought that we would suffer having to care for him but at least he would benefit from our care. Now as I look back I see that it was all the other way round. It was only him that ever really suffered and it was us - Sam, me, Nancy and Elwen - who gained more than I ever believed possible from having and loving such a wonderfully special and beautiful boy."