London Marathon & Grand Princess TA

We are sailing on a 15 day TA (Fort Lauderdale/Southampton) on the Grand Princess from April 9 to April 24 and then flying home on the 26th after two days in London. We booked almost a year ago, but I never thought to check on the date of this year's London Marathon or any other races in the ports we are visiting. I just found out the marathon is on April 25. Of course, it is too late to register, but at least we can be spectators. How great is that!