More than one million revellers are expected to descend on the capital over the next two days for Europe's biggest street festival - the Notting Hill Carnival.

Dancers wearing vibrant costumes will parade along the packed three-and-a-half mile route in west London from 9am today to the sounds of traditional steel drums.

The lines of colourful floats will be accompanied by more than 40 static sound systems and scores of Caribbean food stalls during the event, which is now in its 48th year.

A massive security operation will also be in force with thousands of police officers set to take to the streets.

A total of 5,000 officers will be on duty today, followed by 7,000 officers on Monday, Scotland Yard said.

Police have already arrested 27 people during an operation to crack down on suspected troublemakers ahead of the carnival.

Well over one million people attend the Notting Hill Carnival every year. Given these huge numbers, crime is low. What we want is for those million people to enjoy the event without worrying about the crime and violence that has been caused by the small minority in the past. This has been a summer like no other in London and the carnival is a centrepiece in our capital's event diary. If you're coming to this year's event we want you to have a safe and enjoyable time. Please look after your belongings, and particularly keep an eye on your mobile phone. Almost half of those people who were victims of pickpockets last year had a mobile phone taken."

Police said screenings will take place at entrances to the carnival to scan for weapons.

Last year's event was marred after a 20-year-old man was stabbed towards the end of the festival.

Across London we'll use specialist officers and technology to make it as hard as possible for those people identified through intelligence to travel about. At entry points to carnival we'll make use of intelligence-led stop and search, our status dogs unit and screening wands to scan people for concealed weapons. We have been working hard with all the partners involved to support this year's carnival being an event to remember in this special year for our capital."

During this year's security operation, police cadets will hand out free maps at tube stations on both days of the carnival in an effort to reduce mobile phone thefts.

Mobile users have been warned thieves have previously snatched devices when people have used their phones to search for directions.