The PM's speech, as she was joined by members of the Jewish community from business, the arts, politics, public services and charities.
I am delighted to welcome you all to this special celebration for the Jewish New Year.
Here today, we have people from all parts of our Jewish community and all parts of our society – from business to the arts, from politics to our public services.
We also have some of our country’s greatest philanthropists, leading charities and some of our most outstanding volunteers.
People like the Jewish Volunteering Network Volunteer of the Year Marsha Gladstone; and today’s Point of Light, Avi Dubiner, whose Shabbat Walks have inspired 22,000 visits to hospitals and care homes as Jewish people give their time on the Sabbath to help others in need.
So the first thing I want to say to all of you is: thank you.
And as Prime Minister I want to use the opportunity of this reception to show my personal support and appreciation for everything that you contribute to our country.
Speaking of recognising contributions, I am also pleased that we have now managed to ensure that, within clear guidelines, state schools will be able to claim gift aid on voluntary contributions.
This is something that can benefit not only Jewish State Schools – but all State schools.
And I am grateful to the work of the Partnership for Jewish Schools in helping to resolve this issue.
As we look to the New Year, we look forward to the Centenary of the Balfour declaration in November. Born of that letter, the pen of Balfour, and of the efforts of so many people, is a remarkable country. Of course, there are great challenges in the region - and we will do everything we can to support efforts towards building a two-state solution – and the lasting peace that we all want to see.
But as Prime Minister, I am proud to say that I support Israel.
And it is absolutely right that we should mark the vital role that Britain played a century ago in helping to create a homeland for the Jewish people.
Rosh Hashanah is, of course, a time for reflection – and it is impossible not to think at this time of the threats to our security and the shocking levels of anti-Semitism that we have seen in the last year.
I want you to know that I will always do whatever it takes to keep our Jewish community safe.
Just last week I sat around the Cabinet table with representatives from the Jewish community – and security was the first item on the agenda.
I am proud that this government has given £13.4 million this year alone to support the vital and brilliant work of CST.
But that is not enough on its own.
So it is right we are reviewing our counter-terrorism strategy to ensure the police and security services have all the powers they need – and to ensure that the length of custodial sentences for terrorism-related offences are sufficient to keep people safe.
It is why we are working to reach international agreements that regulate cyberspace to prevent the spread of extremism and terrorist planning – and to get internet companies to do more to remove harmful content from their networks.
And we are establishing a new Commission for Countering Extremism as a statutory body to help fight hatred and extremism in the same way as we have fought racism – because this extremism is every bit as insidious and destructive to our values and we will stop at nothing to defeat it.
We will also continue to fight anti-Semitism wherever we find it.
Through our new definition of anti-Semitism we will call out anyone guilty of any language or behaviour that displays hatred towards Jews because they are Jews.
And we will actively encourage the use of this definition by the police, the legal profession, universities and other public bodies.
But the ultimate way of defeating anti-Semitism is to create an environment that prevents it happening in the first place.
That is one of the reasons why it is so important that we create a proper National Memorial to the Holocaust, together with an accompanying educational centre to teach future generations to fight hatred and prejudice in all its forms.
I want to thank the Chief Rabbi, Sir Peter Bazalgette and all the members of the cross-party UK Holocaust Memorial Foundation - and its partners like the Holocaust Educational Trust - for the work they have been doing to take this forward.
Through the exhibition at the V&A this Summer – as well as wider events across the country - we have now seen over 11,000 responses to the public consultation on the short-listed designs.
And we await with interest the deliberations of the independent Jury that meets this weekend.
Whichever design team is chosen, this national Memorial and Educational Centre will stand next to our Parliament as a permanent reminder of what can happen when a civilised, democratic society allows hatred to go unchecked.
It will say to the world: we will never forget. And it will bring our country together in a national mission to fight hatred for generations to come.
So as you gather together for prayer and celebration at this special time of year, I encourage you to do so with confidence.
Confidence, that together we will keep Jewish people in our country safe and defeat the scourge of anti-Semitism.
And confidence that it is the values that we share – Jewish values, British values - that will in the end prevail.
With that, let me wish you and all your families a sweet New Year.
And as I hand over to the Chief Rabbi to say a few words: let me say to you all: Shana Tova.