Does anyone know if there are specific opening hours for flight connections/security at B gates?

Twice in November, I landed at B/C in the morning and needed to connect to another flight in B/C only to find the checkpoint was closed. It turned what should have been a very comfortable 90-minute layover into almost missing the connection.

On Friday I have a 60-minute connection at Heathrow around 10 am, with a good chance that both flights will be at C gates, and I'm wondering if I should be packing running shoes and a sweatband or if I just had bad luck last month.

Thanks,

EPA