Video report by ITV News Correspondent Neil Connery
PHE has launched new guidance on how to look after your own wellbeing - as well as that of children and other dependants - during strengthened stay-at-home measures.
The guidance offers tips on staying in touch with loved ones using video calls and social media, as well as establishing a healthy sleep pattern or starting a new hobby.
It comes as mental health minister Nadine Dorries - who was herself diagnosed with Covid-19 - also announced an additional £5 million in funding to leading mental health charities to expand their services.
The Duke and Duchess of Cambridge said: "The last few weeks have been anxious and unsettling for everyone.
"We have to take time to support each other and find ways to look after our mental health.
"It is great to see the mental health sector working together with the NHS to help people keep on top of their mental wellbeing.
"By pulling together and taking simple steps each day, we can all be better prepared for the times ahead."
The guidance, which was developed with the input of mental health charities and clinically assured by the NHS, also has points on how to help children manage stress.
Published on PHE's Every Mind Matters page, it includes tips such as being aware of your own reactions around children and creating a new routine for them.
There is also support for those who are already living with a serious mental health problem, such as how to access help from mental health professionals.
PHE said it is issuing guidance to NHS trusts on prioritisation of services and how to maximise use of digital and virtual channels to keep delivering support to patients.
It said NHS mental health providers are also establishing 24/7 helplines.
Announcing additional funding, mental health minister Nadine Dorries said she had felt "anxious and scared" after receiving her diagnosis.
"For those who already suffer with anxiety or other mental health issues this may present new and difficult challenges.
"It's imperative that we stay home if we are to beat coronavirus and save lives.
"I know how important it is that people have support to look after their mental health and this guidance will be of huge value."
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