How to respond to Google Map custom marker popup box press to activate an new activity

I have a Google mapping application that displays one or more markers on the map. I have successfully implemented a custom marker popup that displays details of the location the marker is pointing to. Now I need the application to, when the user presses the details box displayed when the marker is pressed, to launch a new activity that will open the web browser and display details of the location.

I have search the web to find a C# example of using the GoogleMap.OnInfoWindowClickListener which I believe is what I need to implement without any success.

I have spent all day on this and it feels that it should be simple, so I just missing something very obvious.

namespace BedfordBC { using Android.App; using Android.Gms.Maps; using Android.Gms.Maps.Model; using Android.OS; using Android.Widget; using System; using Android.Text; using Android.Text.Style; using Android.Views;

using System.Collections.Generic;

[Activity(Label = "@string/activity_label_mapwithmarkers")]
public class DisplayMap : Activity
{
    private GoogleMap _map;
    private MapFragment _mapFragment;

    //BBC Map stuff
    private List<MapItem> siteDetails = null;  //new List<MapItem>();

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        //Get site details sent from calling screen either single site or 
        // multiple sites if Map button pressed in header of listview

        string siteCount = Intent.GetStringExtra("SiteCount");

        if (siteCount == null) {
            siteDetails = LeisureListAdapter.SelMap;  //Single button in list pressed
        } else
            siteDetails = LeisureServices.SelMap;   //Map button at the top of the list selected

        SetContentView(Resource.Layout.MapLayout);

        InitMapFragment();

        //SetupZoomInButton();
        //SetupZoomOutButton();
    }

    protected override void OnResume()
    {
        base.OnResume();
        SetupMapIfNeeded();
    }

    private void InitMapFragment()
    {
        _mapFragment = FragmentManager.FindFragmentByTag("map") as MapFragment;
        if (_mapFragment == null)
        {
            GoogleMapOptions mapOptions = new GoogleMapOptions()
                .InvokeMapType(GoogleMap.MapTypeNormal)
                .InvokeZoomControlsEnabled(false)
                .InvokeCompassEnabled(true);

            FragmentTransaction fragTx = FragmentManager.BeginTransaction();
            _mapFragment = MapFragment.NewInstance(mapOptions);
            fragTx.Add(Resource.Id.map, _mapFragment, "map");
            fragTx.Commit();
        }
    }

    private void SetupMapIfNeeded()
    {
        if (_map == null)
        {
            _map = _mapFragment.Map;
            if (_map != null)
            {
                //If Header Map button pressed there will be more than one site to add a marker for

                foreach (var  item in siteDetails) {
                    MarkerOptions markerOpt1 = new MarkerOptions();
                    markerOpt1.SetPosition(new LatLng(item.Latitude, item.Longitude));
                    markerOpt1.SetTitle(item.Name);
                    //string snippet = "Address 1 " + System.Environment.NewLine + "Address 2 " + System.Environment.NewLine + "Address 3";
                    SpannableString titleText = new SpannableString(item.Address);
                    //titleText.
                    markerOpt1.SetSnippet (titleText.ToString());
                    _map.AddMarker(markerOpt1);

                }
                // Custom Marker 
                _map.SetInfoWindowAdapter(new CustomMarkerPopupAdapter(LayoutInflater));

                // We create an instance of CameraUpdate, and move the map to it.
                CameraUpdate cameraUpdate = CameraUpdateFactory.NewLatLngZoom(new LatLng(siteDetails[0].Latitude, siteDetails[0].Longitude), 15);
                _map.MoveCamera(cameraUpdate);

            }
        }
    }

}

public class CustomMarkerPopupAdapter : Java.Lang.Object, GoogleMap.IInfoWindowAdapter
{
    private LayoutInflater _layoutInflater = null;

    public CustomMarkerPopupAdapter(LayoutInflater inflater)
    {
        _layoutInflater = inflater;
    }

    public View GetInfoWindow(Marker marker)
    {
        return null;
    }

    public View GetInfoContents(Marker marker)
    {
        var customPopup = _layoutInflater.Inflate(Resource.Layout.CustomMarkerPopup, null);

        var titleTextView = customPopup.FindViewById<TextView>(Resource.Id.custom_marker_popup_title);
        if (titleTextView != null)
        {
            titleTextView.Text = marker.Title;
        }

        var snippetTextView = customPopup.FindViewById<TextView>(Resource.Id.custom_marker_popup_snippet);
        if (snippetTextView != null)
        {
            snippetTextView.Text = marker.Snippet;
        }

        return customPopup;
    }
}

}