Token Literal error when making POST API call

Hi

Wondering if anybody could spot what is wrong with the M query below. I'm trying to pass a query to an API (using POST method).

I'm getting the error 'Token Literal Expected' and when I click show error, it highlights the = sign before the let statement. So it's not very helpful. Using POST to call an API doesn't appear to be very well documented. The key pairs in the body are values from a database which contains parameters for the API. Basic authentication has been configured in settings on the data source (myurl), hence not in the query itself.

=let
url = "http://myurl",
body = "{
"eventID": "167",
"processID": "96",
"project": "SSL",
"version": "004.008.003.007",
"environmentDataRisingEdgeSize": "42",
"environmentDataRisingEdgeCount": "10",
"environmentDataRisingEdgeStart": "0",
"environmentDataRisingEdgeTriggerFrame": "7",
"rawEnvironmentData":"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
"Start Date/Time":"2020-12-01 10:42:04.853",
"End Date/Time":"2020-12-01 10:42:06.853"
}",
Data= Web.Contents(url,[Content=Text.ToBinary(body),Headers=[#"Content-Type"="application/json"]]),
DataRecord = Json.Document(Data),
Source=DataRecord
in
Source