Harare - Eyes closed, frequently fumbling for the right word: this was President Robert Mugabe finally showing his 93 years.In a sunlit room at State House in Harare, Mugabe has given his usual long interview to mark his birthday - but the longtime leader's masterful speaking style was mostly absent.The first part of the interview was broadcast on state ZBC television on Monday night."She is a very strong character, eh?" Mugabe said of his wife Grace. There's growing speculation Grace is being groomed to succeed her husband. The president told interviewer Tazzen Mandizvidza that Grace was "very much accepted by the people". For the first 15 minutes Mugabe spoke extremely quietly - perhaps not in a mutter, but certainly in a very tired voice. As the interview wore on, there were moments where he spoke more strongly. But there were long pauses as his voice fizzled out.He said: "I have been at it [as leader] for a longer period than anyone else and leaders will have to be you know, as it were, given time to develop."Mugabe has been in power in Zimbabwe for nearly 37 years. Recently, there have been frequent questions about his physical fitness to lead Zimbabwe, given a notable stumble on the red carpet in 2015 and other times when he has appeared less than steady on his feet. This interview will only intensify those questions.Watch the video below.