diff --git a/common-lib/src/main/scala/com/gu/mediaservice/lib/DateTimeUtils.scala b/common-lib/src/main/scala/com/gu/mediaservice/lib/DateTimeUtils.scala
index ab43fe1362..f8d2099b9f 100644
--- a/common-lib/src/main/scala/com/gu/mediaservice/lib/DateTimeUtils.scala
+++ b/common-lib/src/main/scala/com/gu/mediaservice/lib/DateTimeUtils.scala
@@ -1,10 +1,11 @@
 package com.gu.mediaservice.lib
 
 import java.time.format.DateTimeFormatter
-import java.time.{Instant, ZoneId, ZonedDateTime}
-
+import java.time.{Instant, LocalDateTime, ZoneId, ZonedDateTime}
 import org.joda.time.DateTime
 
+import java.time.temporal.ChronoUnit
+import scala.concurrent.duration.{DurationLong, FiniteDuration}
 import scala.util.Try
 
 object DateTimeUtils {
@@ -18,4 +19,14 @@ object DateTimeUtils {
 
   // TODO move this to a LocalDateTime
   def fromValueOrNow(value: Option[String]): DateTime = Try{new DateTime(value.get)}.getOrElse(DateTime.now)
+
+  def timeUntilNextInterval(interval: FiniteDuration, now: ZonedDateTime = now): FiniteDuration = {
+    val nowRoundedDownToTheHour = now.truncatedTo(ChronoUnit.HOURS)
+    val millisSinceTheHour = ChronoUnit.MILLIS.between(nowRoundedDownToTheHour, now).toDouble
+    val numberOfIntervals = (millisSinceTheHour / interval.toMillis).ceil.toLong
+    ChronoUnit.MILLIS.between(
+      now,
+      nowRoundedDownToTheHour plusSeconds (interval mul numberOfIntervals).toSeconds
+    ).millis
+  }
 }
diff --git a/common-lib/src/test/scala/com/gu/mediaservice/lib/DateTimeUtilsTest.scala b/common-lib/src/test/scala/com/gu/mediaservice/lib/DateTimeUtilsTest.scala
index bbd67dc8ab..2cce5b07d7 100644
--- a/common-lib/src/test/scala/com/gu/mediaservice/lib/DateTimeUtilsTest.scala
+++ b/common-lib/src/test/scala/com/gu/mediaservice/lib/DateTimeUtilsTest.scala
@@ -4,6 +4,11 @@ import org.joda.time.DateTime
 import org.scalatest.funspec.AnyFunSpec
 import org.scalatest.matchers.should.Matchers
 
+import java.time.ZonedDateTime
+import java.time.temporal.ChronoUnit
+import scala.concurrent.duration.{DurationInt, DurationLong, FiniteDuration}
+
+
 class DateTimeUtilsTest extends AnyFunSpec with Matchers {
   it ("should convert a string to a DateTime") {
     val dateString = "2020-01-01T12:34:56.000Z"
@@ -21,4 +26,28 @@ class DateTimeUtilsTest extends AnyFunSpec with Matchers {
     val actual = DateTimeUtils.fromValueOrNow(None)
     actual shouldBe a[DateTime]
   }
+
+  it ("should return the time until the next instance of the interval relative to the hour"){
+    def toZonedDateTime(timePart: String) = ZonedDateTime.parse(s"2023-11-21T${timePart}Z[Europe/London]")
+    def test(nowTime: String, expectedTime: String, interval: FiniteDuration = 15.minutes) = {
+      DateTimeUtils.timeUntilNextInterval(
+        interval,
+        toZonedDateTime(nowTime)
+      ) shouldEqual ChronoUnit.MILLIS.between(
+        toZonedDateTime(nowTime),
+        toZonedDateTime(expectedTime)
+      ).millis
+    }
+    test(nowTime = "11:11:23.887", expectedTime = "11:15:00.000")
+    test(nowTime = "11:23:23.887", expectedTime = "11:30:00.000")
+    test(nowTime = "11:33:23.887", expectedTime = "11:45:00.000")
+    test(nowTime = "11:50:23.887", expectedTime = "12:00:00.000")
+    test(nowTime = "11:00:00.000", expectedTime = "11:00:00.000")
+    test(nowTime = "11:00:00.001", expectedTime = "11:15:00.000")
+
+    test(nowTime = "11:00:00.001", expectedTime = "11:01:00.000", interval = 1.minute)
+    test(nowTime = "11:00:00.001", expectedTime = "11:02:00.000", interval = 2.minute)
+
+    test(nowTime = "11:01:00.001", expectedTime = "12:00:00.000", interval = 1.hour)
+  }
 }
diff --git a/thrall/app/controllers/ReaperController.scala b/thrall/app/controllers/ReaperController.scala
index e4c860fcc8..1d6bfb19bb 100644
--- a/thrall/app/controllers/ReaperController.scala
+++ b/thrall/app/controllers/ReaperController.scala
@@ -1,7 +1,7 @@
 package controllers
 
 import akka.actor.Scheduler
-import com.gu.mediaservice.lib.ImageIngestOperations
+import com.gu.mediaservice.lib.{DateTimeUtils, ImageIngestOperations}
 import com.gu.mediaservice.lib.auth.Permissions.DeleteImage
 import com.gu.mediaservice.lib.auth.{Authentication, Authorisation, BaseControllerWithLoginRedirects}
 import com.gu.mediaservice.lib.config.Services
@@ -15,7 +15,7 @@ import org.joda.time.{DateTime, DateTimeZone}
 import play.api.libs.json.{JsValue, Json}
 import play.api.mvc.{Action, AnyContent, ControllerComponents}
 
-import scala.concurrent.duration.DurationInt
+import java.time.temporal.ChronoUnit
 import scala.concurrent.{ExecutionContext, Future}
 import scala.jdk.CollectionConverters.collectionAsScalaIterableConverter
 import scala.language.postfixOps
@@ -50,7 +50,7 @@ class ReaperController(
   (config.maybeReaperBucket, config.maybeReaperCountPerRun) match {
     case (Some(reaperBucket), Some(countOfImagesToReap)) =>
       scheduler.scheduleAtFixedRate(
-        initialDelay = 0 seconds,
+        initialDelay = DateTimeUtils.timeUntilNextInterval(INTERVAL), // so we always start on multiples of the interval past the hour
         interval = INTERVAL,
       ){ () =>
         if(store.client.doesObjectExist(reaperBucket, CONTROL_FILE_NAME)) {