I am going to say that the Small Tortoiseshell was my 'Butterfly of the Year' for 2020.
I saw them in the kind of numbers that I have not seen around here for some years and took loads of photos of both those re-appearing in the spring and then again later in the summer. In fact I took so many photos that I am going to limit the ones that I post here to ones taken within walking distance from home, and even then I had trouble whittling them down to a 'reasonable' number.
I saw my first ones on 21st of March, which is pretty average timing for around here, although they did appear with a bit of a bang with the most I have ever seen on my first day of sightings included a number of courting pairs.

- Small Tortoiseshell pair - Wagon Lane 21.03.2020
They were then seen every day that I went out on my daily exercise walk during the first 'lockdown'.

- Small Tortoiseshell - Wagon Lane 24.03.2020

- Small Tortoiseshell - Wagon Lane 26.03.2020

- Small Tortoiseshell - Wagon Lane 03.04.2020

- Small Tortoiseshell pair - Sheldon Country Park 05.04.2020

- Small Tortoiseshell - Wagon Lane 07.04.2020

- Small Tortoiseshell - Wagon Lane 12.04.2020
Given the numbers seen in the spring, both by myself and by reports from elsewhere in the midlands, where was considerable hope for a good summer emergence. The first fresh summer examples were seen flying before the end of May and by early June it was apparent that they were emerging in very good numbers. During June and into July, some of my walks to my local spot at Wagon Lane produced 40-50 plus each time, and this is a pretty small site consisting of a couple of small areas of waste ground to the side of a local city park.

- Small Tortoiseshell - Sheldon Country Park 02.06.2020

- Small Tortoiseshell - Sheldon Country Park 02.06.2020

- Small Tortoiseshell - Wagon Lane 13.06.2020

- Small Tortoiseshell - Wagon Lane 13.06.2020

- Small Tortoiseshell - Wagon Lane 30.06.2020

- Small Tortoiseshell - Wagon Lane 14.07.2020
Apart from those seen within walking distance from home, I also saw plenty at my other local spots around Solihull and at other sites around Warwickshire.
The only times that I went further south last year was to Cornwall in early August where I saw a few (approx. half a dozen) and then to Dorset in early September where I only saw one.
Fingers crossed for the coming year and hoping that we see plenty again this spring.
Cheers,
Neil