Being the owner of a Swedish passport, I have been quite spoiled with never having to issue any visas during all my travels around the world. Until today because all foreigners require a visa to visit India.
The place to get an Indian visa in London is India House, Aldwych, London WC2B 4NA. The operating hours are 08:30 to 12:30 but you're best to be there by 07:30...latest! The queue builds up very fast after that and you would spend the rest of the morning there if not being turned away due to too many applicants.
First you have to queue outside, in the freezing morning, to get a queuing coupon. The small window where they hand out the queuing coupons opens only at 08:30.
After that you are at least let inside and can purchase a warm drink. Inside you wait until your number comes up to hand over all the paperwork.
Make sure you have a pre-filled visa application form, your passport, two passport photos and cash enough for the fee (usually £ 30). If you require a business visa to India make sure to bring a letter both from your company and the Indian company, stating the purpose and duration of your stay. If you have been travelling recently in certain Yellow Fever endemic countries, bring proof of vaccination.
The last waiting exercise is to get back your passport. This process is less organised as the passports come back in batches of 30 and the numbers are shouted out.
All in all it wasn't an as stressed experienced as it might have been, had I arrived only 30 minutes later. There were even some jokes going on about certain embassy staff that were reading the morning paper and drinking tea in the middle of the chaos...