To enter the United Kingdom as a visitor from India, you will need to apply for a Standard Visitor visa. You can apply for a Standard Visitor visa online through the official website of the UK Visas and Immigration (UKVI). The visa application process usually takes around 3 weeks, but during peak seasons, it may take longer.
Please note that visa requirements and regulations are subject to change, so I recommend checking the official UKVI website or contacting the nearest British embassy or consulate in India for the most up-to-date information.