function initialize() {
  if (GBrowserIsCompatible()) {    
    var map = new GMap2(document.getElementById("googlemaps"));
    map.setCenter(new GLatLng(51.5071994, -0.5897238), 16);
    var point = new GLatLng(51.5071994, -0.5897238);
    var marker_headoffice = new GMarker(point);
    GEvent.addListener(marker_headoffice, "click", function() {
    marker_headoffice.openInfoWindowHtml("<div align='center'><strong>Global Security (UK) Ltd.</strong><br />Pegasus Court<br/>27 Herschel Street<br/>Slough<br/>Berkshire<br/>SL1 1PA</div>");
    })
    map.addOverlay(marker_headoffice);
    map.setUIToDefault();   
  }
}