When Pranab Mukherjee became external affairs minister in February 1995, many in the foreign service were unimpressed.
What kind of an image would a short man with a thick Bengali accent convey, they snorted derisively.
Yet in no time, Mukherjee mastered the nuances of foreign policy and won over the sceptics.
As Mukherjee returns to the ministry, the worry is not about what he brings to the job. The worry for the government is to find people to take on his workload.
The UPA has set up 40 Groups of Ministers or Empowered GoMs, most of which Mukherjee has chaired. At any given time, he chairs nearly a dozen GoMs.
He handles a lot of legislative work; acts as a liaison for the Congress with allies and opposition. No wonder then, that he has a 14-hour workday.
As Prime Minister Manmohan Singh and Sonia Gandhi ponder who fills in, both will be aware of how two assassinations shaped Mukherjee's career.
The first was of Indira Gandhi: Mukherjee was a favourite of hers. He appointed Manmohan Singh as RBI governor while he was her finance minister. He was on the same flight as Rajiv Gandhi when news came of her death.
He burst into tears, then messaged the armed service chiefs to meet them at the tarmac. Rajiv's advisor Arun Nehru thought he was positioning himself to take over and advised Rajiv to drop him from his Cabinet.
Mukherjee spent a few years in political wilderness before working his way back into Rajiv's inner circle. He drafted the economic sections of the Congress manifesto for the 1991 Lok Sabha polls and was the certain choice for finance minister were Rajiv to return to power.
But the second assassination occurred. New Prime Minister Narasimha Rao chose Manmohan instead. The rest, as they say, is history.
Ask BJP leaders and even they will tell you Mukherjee has not just a brilliant mind but an encyclopaedic memory.
Perhaps because he has no mass base, he is able to devote much time and energy to work. Aides say his meetings are meticulous, focussed. He does not suffer fools.
The introverted Mukherjee might harbour ambitions of becoming deputy PM. By all accounts, he handles far more work than the last deputy PM, Advani, did.
And he does so without being pompous. Anyone who underestimates him does so at his own risk.