Big Ben rang 40 times in three minutes.
Across the nation, churches joined in the event by also ringing their bells for three minutes.
The initiative was the idea of Turner Prize-winner Martin Creed.
He told BBC Breakfast: “Bells are the loudest acoustic instrument – that’s why they’re used by churches. It’s a piece of music for a special occasion.”
The Coptic Cathedral of St George at The Coptic Orthodox Church Centre UK rang its bells in unison with churches around the country.
The head of the Coptic Orthodox Church in the UK, Bishop Angaelos, said: “2012 has been a mixed year of festive celebrations and economic struggles, and this historic third hosting of the Olympic Games in London brings hope of greater social interaction, hope and prosperity. We celebrate as a nation and as nations together, praying for joy, safety and peace. We also pray for those who are organising, participating and supporting, that God may bless this time for them, and keep this empowering and unifying spirit alive for months and years to come.”
According to the BBC, churches in the Isle of Man and Northern Ireland also took part.Bells rang out in unison at all four parliaments in the UK – the National Assembly for Wales, Stormont, Holyrood and the House of Commons.
The stage is set for tonight’s spectacular opening ceremony at the east London stadium.
Locog is keeping a tight lip on who will have the honour of lighting the Olympic flame during the £27m extravaganza.