No one bothers anymore which is quite sad imo, especially when you see junior members of staff walking around the office in tracksuit bottoms.
Even if the rest of the company doesn’t(including the ceo), as a senior director, i make sure I have on at least a crisp white shirt(sometimes paired with a 3/4 zip jumper or sports jacket) and some chinos on the days I'm in the office. I’ll often dress it down with white trainers, though. The rest of the company doesn’t bother but it makes a difference, particularly in the eyes of clients. Presentation is very important to me, especially these days when no one else bothers.
Sadly tailoring is now associated with car sales, a day at the races or a day in court but I have a couple of well altered suits that get brought out for events that I enjoy wearing.