Continuing on despite serious illness not unusual in politics
HISTORICALLY, political leaders have been wary of admitting to illness in public for fear of it being taken as a sign of weakness that might unnerve supporters.
However, 24 hour news, the decline of a deferential press and the explosion of social media, which can see leaked information spread at an unprecedented rate, means that is no longer a viable option.
Even the notoriously secretive North Korea has recently been forced to acknowledge the health problems of its leader Kim Jong-un, who is apparently suffering from gout.
In the west, the ramifications of it later emerging that details of the illness of a head of state or senior government figure had been suppressed would be devastating for the image of any democratic government claiming openness and transparency.
The world did not know until decades after his death that US president John F Kennedy suffered from Addison's disease and, at the time of the1961 Bay of Pigs crisis and during a crunch meeting with Soviet leader Nikita Khrushchev, was having dilute cocaine injected five times a day into his back muscles.
And wartime US leader Franklin D Roosevelt hid the fact that he was suffering from a range of health problems, including but not confined to: high blood pressure, coronary artery disease and congestive heart failure.
He went on to win the 1944 election, dying a short time later.
Meanwhile, both the last Shah of Iran and French president François Mitterrand managed to suppress the fact they were suffering from terminal cancer towards the end of their time in power.
Closer in proximity and more recently, former secretary of state Mo Mowlam maintained the fiction for nine years before her death that she was suffering from a benign brain tumour when in fact it was malignant. Only her husband and one doctor knew the truth.
She was told just months before Labour swept to power in 1996, with a life expectancy of just three years, but hid the truth from British prime minister Tony Blair and secured the post at the Northern Ireland Office.
Mr Blair himself was famously still British premier when he underwent a heart procedure to correct a continuing "flutter" when there was a recurrence after an earlier treatment for supraventricular tachycardia (SVT).
And three years after Peter Robinson's predecessor DUP leader Ian Paisley was taken gravely ill and described himself as having "walked in death's shadow", he became first minister of Northern Ireland.
In 2000, Scottish first minister Donald Dewar had surgery to repair a leaking heart valve, and was forced to take a three-month break from Parliament, with his deputy first minister Jim Wallace taking over.
He returned to work on 14 August 2000, two months later suffered a fall and a massive brain haemorrhage which was possibly triggered by the anticoagulant medication he was taking after the surgery, dying the following day aged 63.
In the Republic, finance minister Michael Noonan revealed in 2013 that he had been diagnosed with a sarcoma on his right arm and had to undergo surgery and radiotherapy. He continues to recover and work.
A previous incumbent Brian Lenihan had revealed details of his 2009 pancreatic cancer diagnosis and continued to serve until three months before his death at the age of 52.
* Ian Paisley, left, became first minister three years after he 'walked in the shadow of death'
Former prime minister Tony Blair was more open about his health problem than his secretary of state Mo Mowlam
* The Republic's finance minister Michael Noonan has made a good recovery from cancer while continuing in the role
* Donald Dewar had surgery to repair a leaking heart valve
* At the time of the 1961 Bay of Pigs crisis John F Kennedy was having dilute cocaine injected into his back muscles