Stephen Sackur speaks to the former Mexican president Vicente Fox, whose strongly worded Twitter responses to Donald Trump have caused a storm on social media. The new US president has wasted little time delivering on his signature campaign promises. He has already ordered the construction of the contentious wall along the US-Mexican border. The US congress will fund it, but ultimately, Mr Trump says, Mexico must pay. Can Mexico afford to provoke the new US administration?(Photo: Former Mexican President Vicente Fox gestures while speaking during an interview with AFP, 2016. Credit: AFP)