The European Council president quotes John Lennon's Imagine - as the PM talks expat rights.
EU negotiator Michel Barnier says there will be "consequences" from Brexit as negotiations begin.
Jobs and living standards must come first as the UK negotiates its EU exit, the chancellor says.
The UK's political upheaval does not augur well for its tough EU exit talks, Katya Adler writes.
What we learned about the Leave result
The people who will negotiate Brexit
Free trade area, single market and customs union
The European Parliament's 'red lines' on Brexit
Important points in the EU's Brexit negotiation plan
Does Spain have more to lose than the UK?
A guide to how UK will replace EU laws
Can the UK change its mind on Article 50?
How will Brexit affect UK security?
'Brexit divorce could turn ugly'