Some basic accessories are essential:

• Lights. By law you must have a front white light and a rear red light when cycling at night, and a rear reflector and pedal reflectors at all times.
• A lock. Theft is a problem in London so spend as much as you can afford to get a stronger lock (and if possible multiple locks). Always leave your bike in a well-lit and busy place to deter thieves.

Others accessories are just really useful:

• A bell. You'll find pedestrians really appreciate an early, gentle warning of your presence if you're on a shared path – a couple of tinkles when you're still 10 metres or so away works well.
• Mudguards. These will help keep splatters off your clothes.
• A rack and panniers. Panniers are bags that attach onto a rack at the back of your bike. They’re useful because they enable you to be unencumbered while riding. The next best option is a rucksack because this keeps your arms free. Never dangle bags from your handlebars.
• A pump and a spare inner tube or puncture repair kit. Punctures are rare, but it’s good to be prepared.

It’s not compulsory to wear a helmet to cycle in London, but many people choose to. If you do, ensure that your helmet is of good quality and properly fitted.