All mail to Canada is currently facing severe delays with Royal Mail unable to give an estimate of delivery times. The following update in from the Royal Mail website.

Update: 1 August 2020
CANADA DELAYS: All mail being sent from the UK to Canada is facing severe delays because of the on-going impact of COVID-19 and record volumes of traffic being received in Canada. We are processing the mail as normal in the UK, but delays are taking place once the mail reaches the Canadian border. As a result, we are unable to advise on likely delivery times.