WORKING policy
{
  "Version": "2012-10-17",
  "Id": "arn:aws:sqs:eu-west-2:684243278952:test-queue/SQSDefaultPolicy",
  "Statement": [
    {
      "Sid": "Sid1517849186492",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "SQS:SendMessage",
      "Resource": "arn:aws:sqs:eu-west-2:684243278952:test-queue",
      "Condition": {
        "ArnEquals": {
          "aws:SourceArn": "arn:aws:sns:eu-west-2:684243278952:test-topic"
        }
      }
    }
  ]
}