Ignition warning light on ?

I have a 1.8 Mondeo 51 reg. 135,000k miles. I was driving on the motorway when suddenly the ignition warning light went on and I lost all the power for about 10 secs. By that time I had the radio on which continue to play despite that. As I was stopping on the hard shoulder the ignition light went off and all the power was there again! I continue my journey and returned back home later. What's that? Could be something serious?