BM Satires with one line per ID

gistfile1.txt

PREFIX crm: <http://erlangen-crm.org/current/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX thes: <http://collection.britishmuseum.org/id/thesauri/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX bmo: <http://collection.britishmuseum.org/id/ontology/>
PREFIX thesIdentifier: <http://collection.britishmuseum.org/id/>
SELECT DISTINCT ?id (GROUP_CONCAT(?title; SEPARATOR = "|") as ?titles) (GROUP_CONCAT(?name; SEPARATOR = "|") as ?names) (GROUP_CONCAT(?desc; SEPARATOR = "|") as ?descs) (GROUP_CONCAT(?date; SEPARATOR = "|") as ?dates)
    {
        ?object crm:P70i_is_documented_in <http://collection.britishmuseum.org/id/bibliography/294> .
         OPTIONAL {
            ?object crm:P48_has_preferred_identifier ?id }.
           OPTIONAL {
               ?object bmo:PX_physical_description ?desc } .
           OPTIONAL {         
            ?object crm:P108i_was_produced_by ?prodevent.
            ?prodevent crm:P9_consists_of ?prodpart .
            ?prodpart crm:P4_has_time-span ?timespan.
            ?timespan rdfs:label ?date} .
           OPTIONAL {
            ?object crm:P108i_was_produced_by ?prodevent2.
            ?prodevent2 crm:P9_consists_of ?prodpart2 .
            ?prodpart2 crm:P14_carried_out_by ?creator.
            ?creator skos:prefLabel ?name .
            ?creator skos:inScheme thesIdentifier:person-institution}
         OPTIONAL {
            ?object rdfs:label ?title }
    }
GROUP BY ?id

For context see http://cradledincaricature.com/2014/11/20/metadta-for-all-the-british-musuem-satires-part-three/

This "improves" on the previous query (https://gist.github.com/ostephens/d2bd979968e28f62dfca) in that it groups all fields so the query produces only one line per 'preferred ID'.