The following message was sent by Betfair:
"We are contacting you to make you aware of a Betfair Exchange Stream API release on the 10th April from 0700-0730 BST
Please note that during this maintenance release there will be a pause to the Order Stream API lasting <60 seconds between 07:17 – 07:25 BST
During this time the Order Stream API won’t send Order Stream updates but will return the documented 503 status message. The Market Stream API will continue to work as normal."