On April 19th, the Sunday Times accused Boris Johnson of missing five meetings of Cobra, the national crisis committee:
Unusually, Boris Johnson had been absent from Cobra. The committee — which includes ministers, intelligence chiefs and military generals — gathers at moments of great peril such as terrorist attacks, natural disasters and other threats to the nation and is normally chaired by the prime minister.
Johnson went on to miss four further Cobra meetings on the [COVID-19] virus. As Britain was hit by unprecedented flooding, he completed the EU withdrawal, reshuffled his cabinet and then went away to the grace-and-favour country retreat at Chevening where he spent most of the two weeks over half-term with his pregnant fiancée, Carrie Symonds.
The government then published a rebuttal (see related question) later that day, which stated:
Claim - It was unusual for the Prime Minister to be absent from COBR and is normally chaired by the Prime Minister.
Response - This is wrong. It is entirely normal and proper for COBR to be chaired by the relevant Secretary of State. Then Health Secretary Alan Johnson chaired COBR in 2009 during H1N1. Michael Gove chaired COBR as part of No Deal planning. Transport Secretary Grant Shapps chaired COBR during the collapse of Thomas Cook. Mr Hancock was in constant communication with the PM throughout this period.
This response doesn't seem to answer the point about whether it is unusual for the PM to be absent, just that it is often chaired by the relevant Secretary of State. Is the absence of the PM from Cobra meetings common? For example, in the cases noted in the government's response, was the PM present at those Cobra meetings? Perhaps the government has left unsaid that if the PM had been present, he would automatically have been chairing the meeting due to seniority?