Sirens at Queen Elizabeth's Jubilee

[OmniAlert]

I'm watching Queen Elizabeth's jubilee right now on TV and heard an electronic siren going off. Not sure if it's police sirens or anything. Seems to be louder than that and had a tone kinda like the sirens in the Netherlands but the same wail tone instead of going to a lower tone to a higher tone.

The siren seemed to be along the river that goes through London near the London Bridge. Does London have a new electronic siren system?

[Digisirran]

I should say that there isn't any across London. It was only one of the police boat sirens that you heard.

[Daniel]

The London Bridge is in Arizona, but the Tower Bridge is a drawbridge that might have a warning siren.