I received the following message from Betfair:
Hi,
As you may have seen, yesterday afternoon we had some technical difficulties that resulted in the Exchange being unavailable.
We encountered an isolated failure on our underlying storage when running a query handling a large amount of data in our Oracle database. This caused the Exchange to slow down to the point where we had to disable betting and restart the matching engine to ensure safe operation again.
The technical teams have worked overnight to release two key updates which were applied this morning to the exchange database just after 9am to help prevent a reoccurrence. Teams will of course be extra vigilant today and monitoring throughout the day along with further work in the week.
Please accept our apologies for any inconvenience caused.