I've spent a year plus working in a company on the outskirts of Shenton Way in 2004. The building name is Bestway Building located opposite MAS Building. Though the building was very old, the good food in the canteen made up for it.
Due to the international nature of our business, we are required to call different parts of the world and this includes the US, Middle East & Europe. My boss never did insist that I stay back late in the office to make my calls though (We can make the calls from home and claim it from the company). A few months later, a new manager was employed and she started arranging us into shifts just to make sure all overseas markets are covered properly.
Then the stories started to roll in.... after 10pm+, you can hear paper ruffling at the end of the office (All your other colleagues have left and that section's lights are all switched off), you can hear children's laughter as they run along the corridor but you can never see them, and one colleague reported having spoke to a new cleaner lady at 5am+. He commented she was early for work and that he had never seen her before. She smiled and said she had been here for a long time but it's just that he never saw her before. At 7am, the usual cleaner lady came to work and he was puzzled but she confirmed that she was the only cleaner lady employed by the company. Interestingly, she said he's not the first to have seen the "other" cleaner lady.
The shift system only lasted a week before my manager stopped it because she did hear the children's running & laughter herself.