ITAs in London can vary from 1 day to 4 weeks depending on circumstances. The processing times for residence visas are currently being reduced with the introduction of new application handling systems and are very good in comparison with other offices. If your application or residence includes a job offer, it should take about 1 - 2 weeks to be allocated a Case Officer and then about another month or two for processing, checking etc. (if there are no medical or security issues to delay it). For those without a job offer, the waiting time is still 4 - 6 months to be allocated a case officer.