Inherited a site whereby we are unable to delete any content nodes in the back-end.

We get the following error message when attempting to delete a content node.

{
    "Message":"Exceptionhasbeenthrownbythetargetofaninvocation.",
    "StackTrace":"atSystem.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfomethod,Objecttarget,Object[]arguments,SignatureStruct&sig,MethodAttributesmethodAttributes,RuntimeTypetypeOwner)\r\natSystem.Reflection.RuntimeMethodInfo.Invoke(Objectobj,BindingFlagsinvokeAttr,Binderbinder,Object[]parameters,CultureInfoculture,BooleanskipVisibilityChecks)\r\natSystem.Delegate.DynamicInvokeImpl(Object[]args)\r\natumbraco.cms.businesslogic.CMSNode.FireCancelableEvent[T](EventHandler`1cancelableEvent,Objectsender,TeventArgs)\r\natumbraco.cms.businesslogic.CMSNode.Move(CMSNodeparent)\r\natumbraco.cms.businesslogic.web.Document.MoveToTrash()\r\natumbraco.contentTasks.Delete()\r\natumbraco.presentation.webservices.legacyAjaxCalls.Delete(StringnodeId,Stringalias,StringnodeType)",
    "ExceptionType":"System.Reflection.TargetInvocationException"
}

Looking at the network call (/umbraco/webservices/legacyAjaxCalls.asmx/Delete) we are getting the following error

Request format is unrecognized for URL unexpectedly ending in '/Delete'.
[InvalidOperationException: Request format is unrecognized for URL unexpectedly ending in '/Delete'.]
   System.Web.Services.Protocols.WebServiceHandlerFactory.CoreGetHandler(Type type, HttpContext context, HttpRequest request, HttpResponse response) +743714
   System.Web.Services.Protocols.WebServiceHandlerFactory.GetHandler(HttpContext context, String verb, String url, String filePath) +308
   System.Web.Script.Services.ScriptHandlerFactory.GetHandler(HttpContext context, String requestType, String url, String pathTranslated) +89
   System.Web.MaterializeHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +490
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +375

Any ideas on how to resolve this?